What are the factors of 405?

1 Answer
Oct 26, 2016

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, }#