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Assertion (A) : The probability… (Class 10 Maths 2025, Q19)

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MathsCBSE Class 10 · Standard · Board exam 2025, set 30/1/1 · 1 mark · Assertion-reason

CBSE Class 10 Mathematics Standard 2025: question 19

Set in the CBSE Class 10 board exam of 2025, paper 30/1/1, section A, question 19, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q19 · 1 mark · Assertion-reasonCompetency-basedProbability

Assertion (A) : The probability of selecting a number at random from the numbers 1 to 20 is 1.
Reason (R) : For any event E, if P(E) = 1, then E is called a sure event.

  1. (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
  2. (B)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
  3. (C)Assertion (A) is true, but Reason (R) is false.
  4. (D)Assertion (A) is false, but Reason (R) is true.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 30/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

How many of the 20 outcomes are favourable?

Hint 2

What do we call an event whose probability is 1?

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.

  1. Any number picked from 1 to 20 is certainly a number from 1 to 20. So the event is certain and its probability . Assertion (A) is true.

  2. An event with probability 1 is called a sure (certain) event, so Reason (R) is true. It explains why the probability in (A) is 1. So the answer is option (A).

    1 mark

Answer: Option (A)

Where the marks are

  • Recognises the sure event: A and R are both true and R explains A, option (A) (1 mark)

Revise the chapter

  • Chapter: Probability (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Probability, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 30/1/1 (Standard): every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.