Question

The
least number which when decreased by 9 is exactly divisible by 12, 16, 24, 48
is ?

Answer 1

2520 is the lowest.

Start with 9 x 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
This is divisible by all single digit numbers
The 1 is irrelevant.

If the number is divisible by 9 then it is divisible by 3
If the number is divisible by 8 then it is divisible by 2 & 4
If it is divisible by 8 & 9 then it is divisible by 6

This reduces the calculation to 
9 x 8 x 7 x 5
= 2520

Answer 2

2520 IS THE ANSWER IT IS DIVISIBLE BY 12,16,24,48