Question

How many 5 digit flippy numbers are divisible by 15.

Answer 1

Answer:

4

Explanation:

Since it's a flippy number, we can set each digit into ababa

Since it can be divisible by 15, which means it can be divisible by both 5 and 3.

Since it is divisible by 5, the last digit will be either 0 and 5, but it cannot be 0 because 0 cannot be the first digit, so last digit must be 5.

So, ababa --> 5b5b5

It can also be divisible by 3. According to de divisibility rule of 3, if the sum of all digit is divisible by 3 then the number is divisible by 3.

Sum of all digits = 15 + 2b

it's divisible by 3 when b = 0,3,6,9

The answer is 4.

There are 4 such number.