Multiple choice

A bag contains n white and n black balls. Pairs of balls are drawn at random without replacement successively until the bag is empty. If the number of ways in which each pair consists of one white and one black ball is 14,400, then n = _________.

  1. 6

  2. 5

  3. 4

  4. 3

  5. 2
Reveal answer Fill a bubble to check yourself
B Correct answer
AI explanation

If the bag starts with n white and n black balls, the number of ways to form n mixed-color pairs is n factorial multiplied by n factorial. Setting this product equal to 14400, we test the given options and find that 5 factorial is 120. Since 120 multiplied by 120 equals 14400, n must be 5.

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