Skip to content

The number of red balls in a… (Class 10 Maths 2025, Q25)

questionbuddy.in/q/cbse-10-maths-2025-30-6-1-q25-number-red-balls-bag-more

MathsCBSE Class 10 · Standard · Board exam 2025, set 30/6/1 · 2 marks · Very short answer

CBSE Class 10 Mathematics Standard 2025: question 25

Set in the CBSE Class 10 board exam of 2025, paper 30/6/1, section B, question 25, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q25 · 2 marks · Very short answerProbability

The number of red balls in a bag is three more than the number of black balls. If the probability of drawing a red ball at random from the given bag is , find the total number of balls in the given bag.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 30/6/1.

Hints

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

Hint 1

Let the number of black balls be and write the red balls and the total in terms of .

Hint 2

Probability of red = red/total; equate to and cross-multiply.

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. Let black balls ; red balls ; total .

    ½ mark

  2. ½ mark

  3. ½ mark

  4. Total number of balls

    ½ mark

Answer: 69 balls

Where the marks are

  • Expresses total as (½ mark)
  • Forms equation (½ mark)
  • Solves (½ mark)
  • Total = 69 (½ 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 30/6/1 (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.