Question

How many numbers lying between 100 and 1000 can be formed with the digits 0,1,2,3,4,5,if the repetition of the digits is not allowed?

Answer 1

`100`

Explanation:

The number will be a `3` digit number

Let us consider the `3` digits to be `3` boxes `squaresquaresquare` in which the numbers can be placed.

First box can be filled in `5` ways(`1,2,3,4,5`)

Second box can be filled in `5` ways(`0`,or any `4` of (`1,2,3,4,5`) )

Third box can be filled up in `4` ways( The `4` numbers unused in the first `2` boxes)

Therefore, total number of ways=`5*5*4=100`