Q1. [1]
If a digit is chosen at random from the digits 1, 2, 3, 4, 5, 6, 7, 8, 9; then the probability that this digit is an odd prime number is :
- A $\dfrac{1}{3}$
- B $\dfrac{2}{3}$
- C $\dfrac{4}{9}$
- D $\dfrac{5}{9}$
Previously asked in CBSE board exam
2024 30/3/1 Q15
Generated by claude-sonnet-4-6 · 2026-06-15 10:29 · grounding rag
Model Answer
Option A: $\dfrac{1}{3}$
Total outcomes = 9. Odd prime numbers from 1–9 are: 3, 5, 7 → 3 favourable outcomes.
$$P(\text{odd prime}) = \frac{3}{9} = \frac{1}{3}$$
Explanation
Note that 1 is not a prime number, and 2 is the only even prime (not odd). So odd primes in {1,2,…,9} are only 3, 5, 7 — giving 3 favourable outcomes out of 9. A common mistake is including 1 or 2, which would change the answer.
If a question refers to an image, map, graph or diagram that is not shown here, open the Study Guide single page app, go to
Library and find the actual CBSE question paper. The original papers are also available on the CBSE website:
cbse.gov.in.