Find the number of `n` digit numbers, which contain the digits 2 and 7, but not the digits 0, 1, 8, 9.

The number of five digit numbers in which all digits are even, is?

The number of five digit numbers in which all digits are even, is :

Find the number of three-digit numbers which are divisible by 5 and have distinct digits

The number of n digit numbers which consists of the digit 1 and 2 only if each digit is to be used at least once is equal to 510, then n is equal to ________.

The number of 10 digit numbers that can be written by using the digits 2 and 3 is

The number of 10 digit number that can be written by using the digits 2 and 3 is

The number of 5 digit numbers all digits of which are odd is

Find the number of three-digit number in which repetition is allowed and sum of digits is even.