Question

How many telephone connections may be allotted with 8 digits from 0,1,2,3 to 9?

Answer 1

Answer:

Step-by-step explanation:

The remaining digits to be used are 1,3,4,5,6,8,9.

And, we have to select 5 digits out of these eight.

First digit can be anyone of these 7 digits.

So, there are 7 ways of choosing the 1st digit.

Similarly, we may choose 2nd digit in 6 ways, 3rd digit in 5 ways, 4th digit in 4 ways and 5th digit in 3 ways.

By the fundamental principle of multiplication, the required number of ways =(7×6×5×4×3)=2520.