CBSE Class 12 Mathematics sample paper 2026-27: question 17
From the official CBSE sample question paper for 2026-27, section A, question 17, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q17 · 1 mark · MCQProbability
A die is thrown twice. What is the probability that at least one number is 4, given the sum of the numbers appearing is a multiple of 5?
- (A)
- (B)
- (C)
- (D)
Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.
Hints
Open one hint at a time and try again before the next.
Hint 1
List all pairs whose sum is 5 or 10.
Hint 2
Count how many of these pairs contain a 4.
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
Let be 'sum is a multiple of 5'. Then , which has 7 outcomes.
- 1 mark
Let be 'at least one 4'. Then , which has 4 outcomes. So .
Answer: 4/7, option (D)
Where the marks are
- Lists the outcomes and computes the conditional probability (1 mark)
Revise the chapter
- Chapter: Probability (notes, formulas, where marks are lost and every past question)
- Topic: Conditional Probability
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