Discussion

The sum of the prime numbers between 31 and 60 is :

Answer: A

The sum is 280.

List the primes between 31 and 60. Check each odd number for divisibility by 3, 5 and 7 (enough, since \(7^{2} = 49\) and \(8^{2} = 64\)):

37, 41, 43, 47, 53, 59

(33, 39, 45, 51 and 57 are multiples of 3; 35 and 55 of 5; 49 is \(7^{2}\).)

\[ 37 + 41 + 43 + 47 + 53 + 59 = 280 \]

31 itself is prime but is not between 31 and 60; including it gives 311, which is the trap in option B.

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