Question

Which of the following numbers is prime?

133
143
153
163

Answer 1

163 is prime

Answer 2

could you explain how you got that?

Answer 3

To see if it is divisible by 3

add up all the numbers, and if the sum of it is divisible by 3, then the number is divisible by 3.

Answer 4

so for example see if 133 is divisible by 3?

Answer 5

and then test the rest of the options?

Answer 6

1+3+3 = 7

So it is not divisible by 3

doesn't end in 5, or 0 not divisible by 5

Divisible by \(\sf 7\)

So it is not a prime.

Answer 7

153 is divisible by 3, so that is also eliminated

1+5+3 = 9
which is divisible by 3

Answer 8

143

not divisible by 3, 5, 7,

and then aha! Divisible by 11

Answer 9

and all of these are not divisible by 2 because they are all odd.

Answer 10

So now do you get how 163 is the answer? :P

Answer 11

sorry i had to step away for a minute, yes i think i understand that....Thanks!! @TheSmartOne