Multiple choice

An Bag contains 6 red, 4 blue, 2 green and 3 yellow marbles. If four marbles are picked at random, what is the probability that at lest one is blue?

  1. 69/91

  2. 4/15

  3. 29/30

  4. 11/15

  5. none

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Use the complement: the probability of no blue marble is C(11,4)/C(15,4) = 22/91. Therefore, the probability of at least one blue marble is 1 - 22/91 = 69/91.

AI explanation

Use the complementary event method by finding the probability of picking no blue marbles. The total marbles equal 15, and the non-blue marbles equal 9, so the probability of picking 4 non-blue marbles is 9C4 divided by 15C4, which equals 126 divided by 1365. Subtracting this from 1 yields 1239/1365, which simplifies to 69/91.