The number of natural numbers less than 7,000 which can be formed by using the digits 0,1,3,7,9 (repetition of digits allowed) is equal to:
The number of natural numbers less than 7,000 which can be formed by using the digits 0,1,3,7,9 (repetition of digits allowed) is equal to:
a1 |
a2 |
a3 |
Number of numbers=53−1
a4 |
a1 |
a2 |
a3 |
2 ways for a4
Number of numbers=2 53
Required number=53+2 53−1
=374