Let `n` be a natural number such that the division `n-:5` leaves a remainder of 4, and the division `n-:2` leaves a remainder of 1. What must be the units digit of `n` ?

Explanation

`n` is divided by `5` leaving a remainder of `4`
We know, that a number that is divisible by `5` has unit digit `0` or `5`.
``Unit digit of `n=4 or 9`

Also,
`n` divided by `2` leaves a remainder of `1`
` n` is an odd number.
Unit Digit of `n=9`.