If ` 24 a ` is divisible by 9, find the value of `a`

Explanation

A number divisible by `9` should have the sum of its digits equal to a multiple of `9`.
Here,
`2+4+a=9x`
`=>6+a=9x`
`=>(6+a)/9 = x`
`x` is a multiple of `9`
If `a=0,``6/9` is not divisible by `9`
If `a=1,``7/9` is not divisible by `9`
If `a=2,``8/9` is not divisible by `9`
If `a=3,``9/9` is divisible by `9`
So, `3` is the least possible value of `a`.