Problem-Solving and Data Analysis practice question

Answer: 2/5 or .4 or 0.4

The primes from 1 to 20 are 2, 3, 5, 7, 11, 13, 17 and 19, eight in all, so the probability is 8/20 = 2/5.

Common wrong answers

If you answered 9/20

9/20 counts 1 as prime.

If you answered 1/2

1/2 counts the odd numbers.

If you answered 7/20

7/20 misses one prime.

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