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Class 9 Maths: The Mathematics of Maybe, Probability, 8 practice questions with answers

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These are 8 practice questions on Chapter 7, The Mathematics of Maybe: Introduction to Probability, of the new NCERT Class 9 Maths textbook, Ganita Manjari, Part I (First Edition, April 2026). Each has a worked answer and the textbook page it comes from. They cover theoretical probability (favourable outcomes out of all possible outcomes), experimental probability from a record of trials, the sample space of two coins, an event on a spinner, and the 0 to 1 scale. Try each one on paper before you open the answer. Chance and data often go together: averages of groups of different sizes are in the Class 9 Understanding Data questions.

These questions are our own, drafted with AI help. Every number was re-computed by a test script, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

What the chapter says you need

Facts from the NCERT textbook (Ganita Manjari: Mathematics, Textbook for Grade 9, Part I, Chapter 7, printed pages 155 to 173):

Theoretical probability

Question 1. A bag has 3 red and 5 blue marbles. One is picked without looking. What is the probability that it is red? (fraction)

Answer: 3/8. 3 red out of 8 marbles in all: 3/8. (Theoretical probability, page 161.)

Question 2. Eighty cards are numbered 1 to 80, and one is drawn at random. Asha says the probability that its number is a multiple of 9 is 9/80, "because we want multiples of 9". What is her mistake, and what is the right probability? (fraction)

Answer: 1/10; she used 9 instead of the number of favourable cards. The probability is the number of favourable outcomes divided by the number of possible outcomes. The multiples of 9 from 1 to 80 are 9, 18, …, 72, which is 8 cards (9 × 9 = 81 is more than 80). So the probability is 8/80 = 1/10, not 9/80. (Theoretical probability, page 161.)

Question 3. A spinner has 8 equal parts numbered 1 to 8. What is the probability that it stops on a number greater than 5? (fraction)

Answer: 3/8. The numbers greater than 5 are 6, 7 and 8: 3 out of 8, so 3/8. (Page 161; the textbook describes an event such as "the number rolled is greater than 4" as a subset of the sample space on page 167.)

Question 4. Meena tosses two coins together. Find the probability that exactly one of them shows heads. (fraction)

Answer: 1/2. The sample space is {HH, HT, TH, TT}: 4 outcomes. Exactly one head: HT and TH, 2 outcomes. Probability = 2/4 = 1/2. (Sample space of two coins, page 166; the tree diagram, pages 168 and 169, where the textbook finds P(HH) = 1/4 and asks you to work out one head and one tail.)

Experimental probability

Question 5. A coin is tossed 50 times and shows heads 28 times. What is the experimental probability of heads? (decimal)

Answer: 0.56. Heads ÷ tosses = 28 ÷ 50 = 0.56. (Page 160.)

Question 6. A die was thrown 200 times and showed a 6 on 36 of them. What is the experimental probability of a 6? (decimal)

Answer: 0.18. Experimental probability = 36 ÷ 200 = 0.18. (Page 160. The theoretical value for a fair die is 1/6, about 0.17; experimental and theoretical probability can differ, and they tend to come closer as the number of trials grows, page 163.)

The probability scale

Question 7. The chance of rain tomorrow is 0.3. What is the chance of no rain? (decimal)

Answer: 0.7. The two chances add up to 1, so 1 − 0.3 = 0.7. (Probabilities lie between 0 and 1, page 157. The textbook uses the two outcomes {Rain, No Rain} as a sample space on page 166; the rule that the two chances add up to 1 is our own step, not stated in this chapter.)

One more question

Question 8. One card is drawn at random from 12 cards numbered 1 to 12. What is the probability that the number on it is a multiple of 3? (This question is not in the practice set.)

Answer: 1/3. The sample space is {1, 2, ..., 12}, with 12 equally likely outcomes. The event "a multiple of 3" is {3, 6, 9, 12}, 4 outcomes. Probability = 4/12 = 1/3. (Sample space, page 166; event, page 167; theoretical probability, page 161.)

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Sources

All opened and read on 21 October 2026. Page numbers are the printed page numbers of the textbook; printed page = PDF page + 154.

The definitions are from the textbook pages above. The questions, worked answers and checks are our own, and every number was re-computed by script. This guide is general information; follow your teacher and the textbook.