1. how many multiple of 7 that are between 100 and 1000

Solution:
`100/7` is `14` with a remainder of `2`

Smallest multiple of 7 greater than 100 is 15, `(7xx15=105)`

`1000/7` is `142` with a remainder of `6`

Largest multiple of 7 less than 1000 is 142, `(7xx142=994)`

So number of multiples of 7`=142-15+1=128`