By signing in you confirm you are 18 or older, or have your parent’s or guardian’s consent.

NDA 2 2025 Maths, question 104

Topic: Probability

Q104

An urn contains 1010 white and 55 red balls. If two balls are drawn at random, then what is the probability that both the balls are red?

  1. (a) 2/212/21Correct answer
  2. (b) 1/71/7
  3. (c) 4/214/21
  4. (d) 3/73/7

Solution.

Answer: (a) 2/212/21

  1. For two draws without replacement, P(both red)=(5/15)(4/14)=2/21.
  2. Equivalently, C(5,2)/C(15,2)=10/105=2/21.