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A box contains 120 discs… (Class 10 Maths Basic 2025, Q23)

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MathsCBSE Class 10 · Basic · Board exam 2025, set 430/6/1 · 2 marks · Very short answer

CBSE Class 10 Mathematics Basic 2025: question 23

Set in the CBSE Class 10 board exam of 2025, paper 430/6/1, section B, question 23, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q23 · 2 marks · Very short answerProbability

A box contains 120 discs, which are numbered from 1 to 120. If one disc is drawn at random from the box, find the probability that

  1. (i)

    it bears a 2-digit number.

    1 mark
  2. (ii)

    the number is a perfect square.

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 430/6/1.

Hints

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

Hint 1

Probability = favourable outcomes ÷ 120.

Hint 2

Two-digit numbers run from 10 to 99; for squares, list until you pass 120.

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. (i) Total outcomes = 120. Two-digit numbers are 10, 11, …, 99, so their count is .

    .

    1 mark

  2. (ii) Perfect squares from 1 to 120 are 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, i.e. 10 numbers ().

    .

    1 mark

Answer: (i) ; (ii)

Where the marks are

  • Counts 90 two-digit numbers and gets probability (1 mark)
  • Counts 10 perfect squares and gets probability (1 mark)

Revise the chapter

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 430/6/1 (Basic): 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.