Question

How many 9 digit numbers are possible by using the digits 1, 2, 3, 4, 5
which are divisible by 4 if the repetition is allowed?​

Answer 1

Answer:

There are 390625 possibilities.

Step-by-step explanation:

A number is divisible by 4, if its last two digits is divisible by 40.

The 2 digit numbers divisible by 40 (using 1, 2, 3, 4, 5):

12, 24, 32, 44, and 52 (5 two digits)

There is a rule to find the number of possibilities:

(Number of results possible) * (Number of results possible) * ...

There are 5 possibilities for the first 7 digits and 5 possibilities for the last two digits together.

= 5*5*5*5*5*5*5*5 = 5^8 = 390625

If I am wrong, I apologise in advance.