Question

which one is a prime number?

35, 69, 89, 90

Answer 1

try and factor each number in turn
if you cant find any its a prime

Answer 2

eg 35 = 5*7 - not prime

Answer 3

A prime number cannot be divisible by any number except for 1 and itself.

Answer 4

A prime number is a number that can only be divided by one and itself, find which of the numbers only has 1 and itselfs that it can be divided by

Answer 5

handy hint: if you add up the digits of a number until you get 1 digit and its 3,6 or 9 then that number is divisible by 3

Answer 6

foe example take 345 : 3+4+5 = 12 1 +2 = 3 so its divisible by 3
try that on the last 3 numbers in your question

Answer 7

6 + 9 = ?

Answer 8

15

Answer 9

and 1 + 5 = ?

Answer 10

6

Answer 11

- so 69 can be divided by so its not prime

Answer 12

* divided by 3

Answer 13

35 = 5*7, 69 = 3*23, 90 = 2*3^2*5 and 10 = 2*5.

Answer 14

35 = 5 * 7
69 = 3 * 23
90 = 2 * 45
10 = 2 * 5
....and 89 is NOT divisible by 2, 3, 5, or 7 (primes less than the square root of 89)

Answer 15

The prime one is the one that it self and 1 can only go in to it for example 36 would not be prime because 36 and 1 and 6, 2,3,4 and 9 can go into it

Answer 16

so is it 89?

Answer 17

yes very good