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Mathematics — CBSE Class 10 board question

Q1. [1]
The number of red balls in a bag is 10 more than the number of black balls. If the probability of drawing a red ball at random from this bag is $\frac{3}{5}$, then the total number of balls in the bag is :
  1. (a) 50
  2. (b) 60
  3. (c) 80
  4. (d) 40
Previously asked in CBSE board exam
2025 30/4/1 Q5
Generated by claude-sonnet-4-6 · 2026-06-15 10:30 · grounding rag
Model Answer

(d) 25

Wait — let me solve: Let black balls = x, red balls = x + 10. P(red) = (x+10)/(2x+10) = 3/5 → 5(x+10) = 3(2x+10) → 5x+50 = 6x+30 → x = 20. Total = 2(20)+10 = 50.

Answer: (a) 50

Explanation

Set black balls = x, red balls = x + 10, total = 2x + 10. Use P(red) = 3/5 to form the equation and solve for x = 20, giving total = 50. Always set up a variable equation from the probability condition in such problems.

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