Question

How many 4 digit number be made using1,2,3,4 5 6 7 with none of?

Answer 1

Answer:

Step-by-step explanation:

Answer is 840!

This is a question of permutation and combination.

We have to make 4 digit number without repetition using 1,2,3,4,5,6,7.

For this we have to fill 4 spaces ( _ _ _ _) with required numbers.

Now for 1st space, how many possible ways you can fill this space?

In 7 ways, because we have 7 number remaining.

( 7 _ _ _)

Now for 2nd space, how many possible ways we can fill this space?

In 6 ways, because we already used one digit in previous space so only 6 digits are remaining now.

( 7 6 _ _)

Now for 3rd space, how many possible ways we can fil this space?

In 5 ways, because we already used two digis in previous spac8 so only 5 digits are remaining now.

( 7 6 5 _)

At last for 4th space, there ar( 7 6 5 4)

So we have to multiple this to get maximum number of ways to make a 4 digit number without repetition.

7*6*5*4 = 840

There are 840 ways to do that. You you can refer this image.

e 4 possible ways to fill this space because we already used three digits in previous space.