SOLUTION 71 TO 80

71.   Required sum = (2 + 3 + 5 + + 7 +11) =28.

72.   Prime numbers less than 50 are:

  2, 3, 4, 5, 11, 13, 17, 19, 23, 29, 31, 41, 43, 47

Their number is 15.

73.   Clearly, 97 is a prime number.

44.   91 is divisible by 7. So, it is not a prime number.

75.   437 > 22

All prime number less than 22 are 2,  3, 5, 7, 11, 13, 17, 19.

161 is divisible by 7, and 221 is divisible by 13.

 373 is not divisible by ay of the above prime numbers 373 is prime.

76.   551 >24

All prime numbers less than 24 are 2, 3, 5, 7, 11, 13, 17, 19.

77.   Sum of two odd numbers is always even

78.    Product of two odd numbers is always odd.

79.   n³ is odd n is odd and n² is odd.

80.   The least prime numbers is 2.

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