Which of these number does NOT belong to the group? A. 83 B. 91 C 71 D. 97

1 Answer
Apr 2, 2018

The correct answer is #B#. See explanation.

Explanation:

Among the four numbers thare are 3 prime numbers. The only composite number (i.e. the number which is not prime) is #91#.

A number greater than one is prime if it is only divisible by #1# and itself.

Number #91# is not prime because it can be written as:

#91=7*13# ##