JAMB 2003 · UME · Q48

Two dice are thrown. What is the probability that the sum of the numbers is divisible by 3?

Worked solution (try it first)
  1. Two dice give 36 equally likely outcomes, with sums from 2 to 12.
  2. The sums divisible by 3 are 3, 6, 9 and 12.
  3. They occur 2, 5, 4 and 1 times, which is 12 outcomes.
  4. So the probability is 1236=13\frac{12}{36} = \frac13, option B.

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