1
Activity 1 begins with —
💡 Hint:
The first activity.
Explanation:
Ten tosses of a coin.
Class 9 · Maths · Chapter 15 · बिहार बोर्ड (BSEB)CBSE · NCERT 2026-27
Probability
Probability
How to use this page:
1. Read — Activity 1 · Activity 2 · Activity 3 · Activity 4 · Activity 5 · Exercise 15.1, diagram, worked example, board tip
2. Check — each lesson has its own questions; the number follows the lesson
3. Mastery ★ — all of that lesson correct. Redo the wrong ones
4. The memory figure shows one point of empirical probability on a line from 0 to 1.
This page follows the Bihar textbook. Ganita Manjari uses a different order. Progress stays in this browser.
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- 1 Uncertainty and Activity 1
- 2 Activity 2 — groups and the cumulative fraction
- 3 Activities 3 and 4 — a die and two coins
- 4 Trial, event, and the formula
- 5 The sum 1, and the values 0 and 1
- 6 Exercise 15.1
- Chapter winner — every lesson at mastery ★
🎬 Shorts
This chapter has no Short on the channel yet, so ten empty cards are not shown. The notes, diagrams and checks are complete.
📄 PDF download — notes + answer key
Uncertainty and Activity 1
अनिश्चितता और क्रियाकलाप 1 · Textbook 15.1–15.2 · coin
“Probably” gets a numberNotes
Everyday words such as probably, doubt and a fifty-fifty chance are uncertainty. Probability gives that uncertainty a number. The subject began with games of chance and is now used in weather and science too.
Activity 1: toss a coin ten times, count heads and tails, then twenty times, then more. The fraction = number of heads / total tosses. As the trials grow, this fraction moves near 0.5.
Activity 1Activity
Take any coin. Fill the table of ten tosses: total, heads, tails. Write both fractions. Then twenty tosses. Then increase again. Watch the fraction move near 1/2. This is not yet the name of the formula. It is a count.
Worked exampleExample
Question: In 40 tosses, 22 are heads. Find the head fraction.
Formula: fraction = number of heads / total tosses.
Substitution: 22 / 40 = 0.55.
Unit: none. It is a ratio.
10-second revision
- Ten, then twenty, then more tosses
- The fraction divides by the total
- Near 0.5 when the trials are large
Board tip · BSEBBoard tip
Do not leave 22/40 as 22. Show the division. The answer 0.55 is a ratio.
Board tip · CBSEBoard tip
A 0.7 from ten tosses is not yet the rule. Increase the trials, then move near 0.5.
Check your understandingall correct = mastery ★
2
As the tosses increase, the head fraction moves near 0.5.
Explanation:
True — this is what Activity 1 shows.
3
If 40 tosses give 22 heads, the fraction is ______.
💡 Hint:
22/40.
Explanation:
0.55.
4
The unit of this fraction is —
💡 Hint:
Count ÷ count.
Explanation:
There is no unit.
5
Write the three stages of Activity 1 and the remark about 0.5.
Model answer (board format)
Ten tosses, then twenty, then more. Fraction = heads / total. As the trials grow, the fraction moves near 0.5.
Check your answer:
Activity 2 — groups and the cumulative fraction
क्रियाकलाप 2 — समूह और संचयी भिन्न · Group coin · cumulative fraction
Add the groups, then find the fraction againNotes
The printed heading has a spelling slip, but the order is still the second activity. Divide the class into groups of 2 or 3. Each group tosses a coin of the same kind 15 times. Write cumulative heads and tails on the board.
The next group adds its count to the earlier sum and finds the fraction on the new total. As the tosses grow, the columns move near 0.5. This is not the die activity. The die comes next.
Activity 2Activity
Use a coin of one value in every group, so the tosses count as one coin. The first row is the fraction of its own 15 tosses. The second row is the fraction of the sum of both groups. That is what cumulative means.
Worked exampleExample
Question: The first group has 6 heads and 9 tails. The second has 8 heads and 7 tails. Find the cumulative head fraction.
Formula: cumulative fraction = total heads / total tosses.
Substitution: heads = 6 + 8 = 14. Tosses = 30. 14 / 30 = 0.466….
Unit: none.
10-second revision
- Each group tosses 15 times
- The fraction is on the new total
- A larger total moves near 0.5
Board tip · BSEBBoard tip
Do not find the second group’s fraction on its own 15 only. Add the earlier sum.
Board tip · CBSEBoard tip
Do not call this Activity 3. The die has not come yet.
Check your understandingall correct = mastery ★
1
In Activity 2 each group tosses —
💡 Hint:
The group coin.
Explanation:
A coin 15 times.
2
A cumulative fraction includes the sum of the earlier groups.
Explanation:
True.
3
With 6 + 8 heads and 30 tosses, the heads are ______.
💡 Hint:
The sum.
Explanation:
14. The fraction is 14/30.
4
Why is a cumulative fraction different from one group’s own fraction? Write one line on the sum of 6 and 8.
Model answer (board format)
The cumulative fraction is 14/30, not only 8/15. The earlier group is added.
Check your answer:
Activities 3 and 4 — a die and two coins
क्रियाकलाप 3 और 4 — पासा और दो सिक्के · Die 1/6 · two coins
A die near 1/6, two coins and three fractionsNotes
Activity 3: throw a die 20 times, then 40. The fraction of each score from 1 to 6 moves near 1/6 when the trials are large. Add groups the way the coin groups were added. A die is a balanced cube with 1 to 6 on the faces.
Activity 4: toss two coins together ten times, then more. No head, one head, two heads. For a large count the fractions are about 0.25, 0.5 and 0.25.
Activity 3, then 4Activity
Do not change the order. First one die. Six columns in the table. Then two coins together. Three columns: 0 heads, 1 head, 2 heads. Write their own fractions. Do not force 1/6 and 0.25 onto a small number of throws.
Worked exampleExample
Question: In 60 throws the score 3 appeared twelve times. Find the fraction and compare it with 1/6.
Formula: fraction = (times 3 appeared) / (total throws). 1/6 ≈ 0.167.
Substitution: 12 / 60 = 0.2. This is near 0.167, not equal.
Unit: none.
10-second revision
- A die moves near 1/6
- Two coins are about 0.25, 0.5, 0.25
- Do not treat a small trial as exact
Board tip · BSEBBoard tip
Writing 12/60 = 0.2 as 1/6 is hasty. It is near, not the same.
Board tip · CBSEBoard tip
The three fractions of two coins should add near 1. Leaving out one column spoils the sum.
Check your understandingall correct = mastery ★
1
Activity 3 moves each die score, for large trials, near —
💡 Hint:
Six faces.
Explanation:
1/6.
2
Activity 4 tosses two coins together.
Explanation:
True.
3
If score 3 appears 12 times in 60 throws, the fraction is ______.
💡 Hint:
12/60.
Explanation:
0.2.
4
For a large count of two coins, the two-head fraction is about —
💡 Hint:
0.25, 0.5, 0.25.
Explanation:
About 0.25.
5
In 200 tosses: two heads 50, one head 100, no head 50. Write the three fractions and the sum.
Model answer (board format)
50/200 = 0.25, 100/200 = 0.5, 50/200 = 0.25. The sum is 1. There is no unit.
Check your answer:
6
Activity 3 comes after Activity 4.
Explanation:
False — the die is 3, two coins are 4.
Trial, event, and the formula
परीक्षण, घटना और सूत्र · Activity 5 · empirical probability
How often it happened, divided by the totalNotes
A trial is an action that produces an outcome. One toss is a trial. One throw is a trial. One simultaneous toss of two coins is also a trial. The outcomes are head, tail, or 1 to 6. An event is a collection of some outcomes. The event of an even score contains 2, 4 and 6.
Activity 5 says: from the table of Activity 3 find the probability of the score 3, and see how it changes as the trials grow. The formula is P(E) = (trials in which E happened) / (total trials). For convenience the book just writes probability.
Activity 5Activity
Open your own table from Activity 3. Count of score 3 ÷ total throws. Write the fraction on the first 20 throws, then on 40. The changing number is the empirical probability. Do not give it a new number. This is the fifth activity.
Worked exampleExample
Question: In 1000 tosses there are 480 heads and 520 tails. Find both probabilities.
Formula: P(E) = (trials in which E happened) / (total trials).
Substitution: P(heads) = 480/1000 = 0.48. P(tails) = 520/1000 = 0.52.
Unit: none. The sum is 1.00.
10-second revision
- A trial is one action
- An event is a collection of outcomes
- P(E) = favourable / total
Board tip · BSEBBoard tip
Changing 480/1000 into a percent is not the first answer of this chapter. Keep 0.48 or the fraction.
Board tip · CBSEBoard tip
An even score is not one outcome. It is an event of three outcomes: 2, 4, 6.
Check your understandingall correct = mastery ★
1
P(E) equals —
💡 Hint:
Divide by the total.
Explanation:
Favourable / total.
2
The event of getting an even score has three outcomes.
Explanation:
True — 2, 4 and 6.
3
For 480 heads and 1000 tosses, P(heads) = ______.
💡 Hint:
480/1000.
Explanation:
0.48.
4
Activity 5 returns to which table?
💡 Hint:
The die score 3.
Explanation:
Activity 3.
5
Write one line each for trial, outcome and event. Also check the sum of 480 and 520.
Model answer (board format)
A trial is an action. An outcome is its result. An event is a collection of some outcomes. 0.48 + 0.52 = 1.
Check your answer:
The sum 1, and the values 0 and 1
योग 1, और 0 तथा 1 · Impossible · certain · complementary event
The ends are includedNotes
When two events split every trial exactly once, their values add to 1. Heads and tails are like that. Probability runs from 0 to 1, both ends included. If no student has that weight, the probability is 0. If every student meets the condition, the probability is 1.
A value above 1 or below 0 is a calculation error. Writing 100 as a percent is not the answer of this formula.
Worked exampleExample
Question: Of 200 students, 135 like the subject. Find the probabilities of like and dislike.
Formula: P = count / 200. Dislike = 1 − like, when together they are all the students.
Substitution: P(like) = 135/200 = 0.675. P(dislike) = 65/200 = 0.325. The sum is 1.
Unit: none.
10-second revision
- 0 is impossible, 1 is certain
- A complementary event adds to 1
- 135/200 = 0.675
Board tip · BSEBBoard tip
Do not treat 65 as the total and write 65/135. The total is 200.
Board tip · CBSEBoard tip
1.2 is not a probability. Check the division again.
Check your understandingall correct = mastery ★
1
The probability of an impossible event is —
💡 Hint:
Not even once.
Explanation:
0.
2
A certain event has probability 1.
Explanation:
True.
3
135/200 = ______.
💡 Hint:
Divide.
Explanation:
0.675.
4
If P = 0.675 is “like”, what is “dislike”? Check the sum.
Model answer (board format)
Dislike = 1 − 0.675 = 0.325. The sum is 1. There is no unit.
Check your answer:
Exercise 15.1
अभ्यास 15.1 · Only Exercise 15.1 · questions 9 and 10 are activities
One exercise, thirteen questionsNotes
The only exercise of this chapter is 15.1. Later pages are an answers appendix, not new exercises. In each question find the total trials, then the favourable count. P = favourable / total.
In the family table, check that the three probabilities add to 1. In the 200 coin trials, take the row of two heads. In the opinion poll of 135 and 65, the total is 200.
Exercise 15.1 in orderActivity
1) The probability of not hitting a boundary. 2) Families with two children, number of girls, sum 1. 3) A student born in August. 4) Three coins, 200 times, two heads. 5) The income and vehicle table. 6) The marks table. 7) Likes or dislikes statistics. 8) An engineer’s distance, empirical. 9) Count vehicles at the gate. This is an activity, not a new number. 10) A three-digit number divisible by 3. This is an activity too. 11) A flour bag above 5 kg. 12) The sulphur dioxide interval. 13) Blood group AB.
Worked exampleExample
Question: In 30 balls a boundary came 8 times. Find the probability that a boundary did not come.
Formula: P(not) = (total − favourable) / total.
Substitution: (30 − 8) / 30 = 22/30 = 0.733….
Unit: none.
10-second revision
- Only Exercise 15.1
- Questions 9 and 10 are not new numbers
- Complement = (total − favourable) / total
Board tip · BSEBBoard tip
Not hitting a boundary is not 8/30. It is 22/30. Read the wording of the question.
Board tip · CBSEBoard tip
Do not turn appendix Exercise 1.1 into a question of this chapter. That is the answers section.
Check your understandingall correct = mastery ★
1
If 8 boundaries come in 30, the probability of no boundary is —
💡 Hint:
The remaining balls.
Explanation:
22/30.
2
Questions 9 and 10 of Exercise 15.1 are not called Activity 6 and 7.
Explanation:
True — they are unnumbered activities inside that same exercise.
3
The decimal of 22/30 is about ______.
💡 Hint:
22 ÷ 30.
Explanation:
About 0.733.
4
The only exercise of this chapter is —
💡 Hint:
Before the summary.
Explanation:
15.1.
5
Of 200 students, 135 like it. Write both probabilities and the sum.
Model answer (board format)
135/200 = 0.675 and 65/200 = 0.325. The sum is 1. There is no unit.
Check your answer:
6
Probability can be 1.5 if the trials are large.
Explanation:
False — the value stays between 0 and 1.
❓ Full question bank — with answers and explanations — 66 questions
Pick a type. The 30 lesson checks are separate — each lesson has as many as its topic needs. All correct earns mastery ★.
BSEB modelpractice · not annual60 tried · 0 correctMultiple choiceMCQ130 tried · 0 correctTrue / falseTrue / false80 tried · 0 correctFill in the blanksFill80 tried · 0 correctMatchMatch20 tried · 0 correctAssertion–reasonAssertion–reason50 tried · 0 correctBalancingBalancing40 tried · 0 correctIdentifyIdentify20 tried · 0 correctShort and longVSA, SA, LA120 tried · 0 correctCBSE-stylenot a PYQ60 tried · 0 correct
No question is marked as a verified past paper. The BSEB set is a model for practice. CBSE items are CBSE-style, not a copy of any year’s paper.
Multiple choice
0/13Pick one option. A wrong try brings a hint.
1
P(E) is —
💡 Hint:
Divide by the total trials.
Explanation:
Favourable / total.
2
For large tosses the head fraction moves near —
💡 Hint:
Activity 1.
Explanation:
0.5.
3
Each die score, for large trials, moves near —
💡 Hint:
Six faces.
Explanation:
1/6.
4
Two heads on two coins are about —
💡 Hint:
Activity 4.
Explanation:
0.25.
5
An impossible event is —
💡 Hint:
Not even once.
Explanation:
0.
6
A certain event is —
💡 Hint:
Every trial.
Explanation:
1.
7
480/1000 equals —
💡 Hint:
Divide.
Explanation:
0.48.
8
135/200 equals —
💡 Hint:
Like.
Explanation:
0.675.
9
If 8 boundaries come in 30, the probability of none is —
💡 Hint:
The rest.
Explanation:
22/30.
10
Activity 2 is —
💡 Hint:
15 tosses.
Explanation:
The group coin.
11
Activity 5 returns to —
💡 Hint:
Score 3.
Explanation:
Activity 3.
12
The exercise of this chapter is —
💡 Hint:
One, before the summary.
Explanation:
Only 15.1.
13
The unit of probability is —
💡 Hint:
A ratio.
Explanation:
There is no unit.
True or false
0/81
Probability can be greater than 1.
Explanation:
False — between 0 and 1.
2
Heads and tails add to 1 when together they are every toss.
Explanation:
True.
3
Activity 4 is the die.
Explanation:
False — 4 is two coins. The die is 3.
4
An event can be one outcome or a collection of several outcomes.
Explanation:
True — an even score is three outcomes.
5
Questions 9 and 10 are Activity 6 and 7.
Explanation:
False — they sit inside Exercise 15.1.
6
A cumulative fraction leaves out the earlier sum.
Explanation:
False — it adds and then finds the new fraction.
7
0 is an impossible event.
Explanation:
True.
8
The unit of 22/40 = 0.55 is the centimetre.
Explanation:
False — a ratio has no unit.
Fill in the blanks
0/81
22/40 = ______.
💡 Hint:
Divide.
Explanation:
0.55.
2
6+8 heads = ______.
💡 Hint:
Cumulative.
Explanation:
14.
3
12/60 = ______.
💡 Hint:
The die.
Explanation:
0.2.
4
480/1000 = ______.
💡 Hint:
Heads.
Explanation:
0.48.
5
520/1000 = ______.
💡 Hint:
Tails.
Explanation:
0.52.
6
135/200 = ______.
💡 Hint:
Like.
Explanation:
0.675.
7
1 − 0.675 = ______.
💡 Hint:
Dislike.
Explanation:
0.325.
8
The numerator of (30−8)/30 is ______.
💡 Hint:
The remaining balls.
Explanation:
22.
Match
0/21
Match the activity with its job.
Column B: A. Two coins · B. One coin, from ten onward · C. Cumulative group coin · D. A die
1. 1
2. 2
3. 3
4. 4
Explanation:
1 is your coin, 2 is the group, 3 is the die, and 4 is two coins.
2
Match the value with its meaning.
Column B: A. A large coin experiment · B. Impossible · C. Certain · D. One die score
1. 0
2. 1
3. 1/6
4. 0.5
Explanation:
0 is impossible, 1 is certain, 1/6 is a die score, and 0.5 is the coin.
Assertion–reason
0/5Check both statements, then see whether the reason explains the assertion.
1
Assertion (A): P(E) divides favourable trials by the total.
Reason (R): Empirical probability is a ratio of counts.
Explanation:
Both are true and R is the reason.
2
Assertion (A): For large tosses, heads move near 0.5.
Reason (R): Each die score also moves near 0.5.
Explanation:
A is true. R is false — the die moves near 1/6.
3
Assertion (A): Probability lies between 0 and 1.
Reason (R): 1.5 is also allowed when the trials are large.
Explanation:
A is true. R is false.
4
Assertion (A): Question 9 is Activity 6.
Reason (R): Questions 9 and 10 are activities inside Exercise 15.1.
Explanation:
A is false. R is true.
5
Assertion (A): Heads 0.48 and tails 0.52 add to 1.
Reason (R): The two events split every toss exactly once.
Explanation:
Both are true and R is the reason.
Coefficient practice
0/4These are not results of this maths chapter. They are only coefficient practice for H2 + O2 → H2O.
1
This is coefficient practice, not a result of this maths chapter. Fill coefficients for H2 + O2 making H2O (blank = 1). This is not a probability result.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
2
This is coefficient practice, not a result of this maths chapter. Fill coefficients for H2 + O2 making H2O (blank = 1). Match the hydrogen count.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
3
This is coefficient practice, not a result of this maths chapter. Fill coefficients for H2 + O2 making H2O (blank = 1). Match the oxygen count.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
4
This is coefficient practice, not a result of this maths chapter. Fill coefficients for H2 + O2 making H2O (blank = 1). A blank coefficient is 1.
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
Classify
0/21
Place each value on its experiment.
About 0.5
About 1/6
Two heads about 0.25
Even scores 2, 4, 6
Explanation:
0.5 is the coin. 1/6 and the even scores are the die. 0.25 is two coins.
2
Place each job on its number.
Ten tosses
A die 20 times
Balls and boundaries
Cumulative groups
Explanation:
Ten tosses are 1, the die is 3, the boundary is Exercise 15.1, and cumulative groups are 2.
Very short answer
0/51
Write the formula for P(E).
Model answer (board format)
P(E) = (trials in which E happened) / (total trials).
Check your answer:
2
Write the values for impossible and certain.
Model answer (board format)
Impossible is 0. Certain is 1.
Check your answer:
3
22 heads, 40 tosses. Write the fraction.
Model answer (board format)
22/40 = 0.55. There is no unit.
Check your answer:
4
What is a trial?
Model answer (board format)
An action with one or more outcomes.
Check your answer:
5
Write the outcomes of the even-score event.
Model answer (board format)
2, 4 and 6.
Check your answer:
Short answer
0/41
480 heads and 520 tails, total 1000. Write both probabilities and the sum.
Model answer (board format)
0.48 and 0.52. The sum is 1. There is no unit.
Check your answer:
2
135 like, 65 dislike, total 200. Write both values.
Model answer (board format)
0.675 and 0.325. The sum is 1.
Check your answer:
3
8 boundaries in 30 balls. Write the probability that one did not come.
Model answer (board format)
(30−8)/30 = 22/30.
Check your answer:
4
Why keep 12/60 apart from 1/6? Write both values.
Model answer (board format)
12/60 = 0.2 and 1/6 ≈ 0.167. They are near, not equal.
Check your answer:
Long answer
0/31
Write Activities 1 to 5 in one line each. Then give the formula for P(E).
Model answer (board format)
1 coin from ten onward. 2 cumulative group fraction. 3 die. 4 two coins. 5 the changing probability of score 3. P(E) = favourable / total.
Check your answer:
2
Explain 0, 1 and a complementary event. Show the sums for 480, 520 and for 135, 65.
Model answer (board format)
0 is impossible, 1 is certain. A complement adds to 1. 0.48+0.52=1. 0.675+0.325=1. There is no unit.
Check your answer:
3
What do questions 1, 7, 9 and 10 of Exercise 15.1 ask? Why not give 9 and 10 a new activity number?
Model answer (board format)
1 is no boundary. 7 is like and dislike. 9 is vehicles at the gate. 10 is a three-digit number. They are activities inside the exercise, not Activity 6 or 7.
Check your answer:
BSEB model paper · practice
0/6This model set is for practice. It is not a question from any year’s annual examination. Annual questions will be added only when a source page is available.
1
22/30 belongs to which situation?
💡 Hint:
The remaining balls.
Explanation:
A boundary did not come.
2
Cumulative 14 heads and 30 tosses give —
💡 Hint:
The sum.
Explanation:
14/30.
3
0.48 + 0.52 = ______.
💡 Hint:
Complement.
Explanation:
1.
4
The answers appendix after Exercise 15.1 is a new chapter exercise.
Explanation:
False — those are answers of the whole book. The exercise of this chapter is only 15.1.
5
1000 tosses, 480 heads. Write P(heads), P(tails) and the unit.
Model answer (board format)
0.48 and 0.52. There is no unit. It is a ratio. The sum is 1.
Check your answer:
6
This is coefficient practice, not a result of probability. Balance H2 + O2 making H2O by filling coefficients (blank = 1).
H2 + O2 → H2O
Explanation: 2H2 + O2 → 2H2O
CBSE-style questions
0/6These are competency-based practice questions. They are not copies of a CBSE paper.
1
Which idea gives a number to “it may rain”?
💡 Hint:
Past days.
Explanation:
Empirical probability.
2
A student writes 8/30 for no boundary. The correction is —
💡 Hint:
The remaining balls.
Explanation:
22/30.
3
Assertion (A): For large trials a coin moves near 0.5.
Reason (R): So every result of ten tosses will be exactly 0.5.
Explanation:
A is true. R is false — small trials still move.
4
If the probability is 2, the event is twice certain.
Explanation:
False — a value above 1 does not occur in this chapter.
5
At a bus stop, 20 of 50 buses were late. Write the probability that a bus was on time. What is the unit?
Model answer (board format)
P(on time) = (50−20)/50 = 30/50 = 0.6. There is no unit.
Check your answer:
6
At the school gate, 18 of 40 vehicles were two-wheelers. Write P(two-wheeler) in the style of question 9. Why not call it Activity 6?
Model answer (board format)
18/40 = 0.45. It is an activity inside Exercise 15.1, not a new number.
Check your answer:
🏛️ Board exam corner — Bihar Board (BSEB)— CBSE
Switch board with BSEB | CBSE above. The lessons follow the same NCERT chapter.
BSEB model · practiceBoard tip
This page has no verified annual-exam question, because no source page has been added. The model set below is practice in the board pattern.
🏛️ Model questions on one page →
The verified label will be used only when a source page for the question is available.
CBSE-style · competency-based
These are case and assertion-reason practice items. Do not treat them as past CBSE questions.
🔁 Spaced review — today’s questions
Wrong questions return soon; correct ones return after a few days.
🧠 What you learned + equation sheet
What you learned
- A trial is an action with one or more outcomes.
- An event is a collection of some outcomes.
- P(E) = (trials in which E happened) / (total trials).
- The cumulative coin fraction moves near 0.5 when the trials are large.
- Each die score moves near 1/6 when the trials are large.
- Probability lies between 0 and 1, both ends included. Impossible is 0, certain is 1.
| What | Keep this |
|---|---|
| Formula | P(E) = favourable / total |
| Coin | near 0.5 |
| Die | near 1/6 |
| Two coins | near 1/4, 1/2, 1/4 |
| Impossible | 0 |
| Certain | 1 |
The notes are original writing. The textbook was used only for activity order and numbers. “Verified” will be used only on a question that has a source page.