Question

What are the factors of 405?

Answer 1

factors `{1,3,9,15,27,45,81,135, 405, }`

Explanation:

A factor of a number is a number that divides exactly into that number eg. 4 is a factor of 16.

To find factors try and pair them up.

for 405

`1xx405=405 :. 1 & 405` are factors

5 divides into 405 so:

`5xx81=405`

now since `81` is a factor and NOT a prime number all the other factors of `81` must be factors of `405`

we have 3, 9, 27
now find pairs.

`3xx135 =405`

`9xx45`

`27xx15`

now check other combinations of the factors

`3xx81=243` not a factor; once we are half way there are no more factors.Similarly for all other combinations.

factors `{1,3,9,15,27,45,81,135, 405, }`