A number is selected at random between 20 and 30, both numbers inclusive. Find the...

JAMB 1993

A number is selected at random between 20 and 30, both numbers inclusive. Find the probability that the number is a prime

A. \(\frac{2}{11}\)
B. \(\frac{5}{11}\)
C. \(\frac{6}{11}\)
D. \(\frac{8}{11}\)

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Correct Answer: Option A

Explanation

Possible outcomes are 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30. Prime numbers has only two factors

itself and 1

The prime numbers among the group are 23, 29. Probability of choosing a prime number

= \(\frac{\text{Number of prime}}{\text{No. of total Possible Outcomes}}\)

= \(\frac{2}{11}\)

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