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A box contains 20 discs… (Class 10 Maths Basic 2023, Q24)

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MathsCBSE Class 10 · Basic · Board exam 2023, set 430/6/1 · 2 marks · Very short answer

CBSE Class 10 Mathematics Basic 2023: question 24

Set in the CBSE Class 10 board exam of 2023, paper 430/6/1, section B, question 24, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q24 · 2 marks · Very short answerProbability

A box contains 20 discs which are numbered from 1 to 20. If one disc is drawn at random from the box, then find the probability that the number on the drawn disc is a

  1. (i)

    2-digit number

    1 mark
  2. (ii)

    number less than 10

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 430/6/1.

Hints

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

Hint 1

Count the favourable discs out of 20 in each case.

Hint 2

2-digit numbers start from 10 and go up to 20 — count carefully including both ends.

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. Total outcomes = 20. (i) 2-digit numbers are 10, 11, …, 20, i.e. 11 numbers.

    1 mark

  2. (ii) Numbers less than 10 are 1, 2, …, 9, i.e. 9 numbers.

    1 mark

Answer: (i) 11/20; (ii) 9/20

Where the marks are

  • (i) P(2-digit number) = 11/20 (1 mark)
  • (ii) P(number less than 10) = 9/20 (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 paper2023 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.