Question

In how many ways can 4 digits are selected out of 10 digits 10 as to include the largest number

Answer 1

Answr:

Step-by-step explanation:

For a number to be even, the units number should be 0, 2, 4, 6 and 8

Case 1 - We select 0 in units place. The remaining 3 numbers can be selected from 1, 2, 3, 4, 5, 6, 7, 8 and 9 in 9C3 ways. And these 3 numbers can be arranged in 3! ways.

So total ways = 9C3 * 3! = 9P3 = 9*8*7 = 504 ways.

Similarly, we can fix 2, 4, 6, 8 => 4 more ways.

So the total number of even 4-digit numbers = 504 + 504 + 504 + 504 + 504 = 2520

Answer 2

2520 is the largest number