Question

Which of the following is a prime number ?
A. 33 B. 81
C. 93 D. 97

mentally ?

Answer 1

@91004775

Answer 2

Again, prime just means only divisible by one and itself.

Which number is not divisible by anything other than 1 and itself? try dividing by 2, 3, 4, etc.

Note there is a rule for a number being divisible by three - the digits add up to a multiple of three.

What do the digits of 33 add up to? 81? 93?

Answer 3

For 33: 3+3 =

81: 8+1 =

93: 9+3 =

Answer 4

all but one of those option is divisible by three