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10 identical blocks are marked… (Class 12 Maths 2025, Q25a)

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MathsCBSE Class 12 · Board exam 2025, set 65/7/1 · 2 marks · Very short answer

CBSE Class 12 Mathematics 2025: question 25(a)

Set in the CBSE Class 12 board exam of 2025, paper 65/7/1, section B, question 25(a), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q25(a) · 2 marks · Very short answerProbability

10 identical blocks are marked with '0' on two of them, '1' on three of them, '2' on four of them and '3' on one of them and put in a box. If X denotes the number written on the block, then write the probability distribution of X and calculate its mean.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 65/7/1.

Hints

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

Hint 1

List each number that can be drawn and count how many blocks carry it.

Hint 2

Mean .

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. X can take the values 0, 1, 2, 3.

    ½ mark

  2. Probability distribution:

    X0123
    P(X)
    1 mark

  3. Mean

    ½ mark

Answer: P(X=0,1,2,3) = 2/10, 3/10, 4/10, 1/10; Mean = 7/5 = 1.4

Where the marks are

  • Correct values of X (½ mark)
  • Correct probabilities (1 mark)
  • Mean = 7/5 (½ 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 65/7/1: 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.