Multiple choice

A box contains 21 balls numbered 1 to 21. A ball is drawn and then another ball is drawn without replacement. What is the probability that both balls are even numbered?

  1. $\(\frac{5}{8}\)$
  2. $\(\frac{5}{7}\)$
  3. $\(\frac{3}{14}\)$
  4. $\(\frac{3}{16}\)$

  5. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

From 1 to 21, there are 10 even numbers (2, 4, 6, 8, 10, 12, 14, 16, 18, 20). Probability of first ball being even = 10/21. Without replacement, 9 even balls remain out of 20 total. Probability of second ball being even = 9/20. Combined probability = (10/21) × (9/20) = 90/420 = 3/14.

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