Five digit numbers are formed using the digits 1 ,   2 ,   3 ,   5 ,   7 with repetitions and are written in descending order with serial numbers. For example, the number 77777 has serial number 1 . Then the serial number of 35337 is

Step-by-step solution

Given, Five digit numbers are formed using the digits 1 ,   2 ,   3 ,   5 ,   7 with repetitions and are written in descending order with serial numbers, Now number of 5 digit numbers starting with digit 1 will be = 5 × 5 × 5 × 5 = 625 Number of 5 digit numbers starting with digit 2 will be = 5 × 5 × 5 × 5 = 625 Number of 5 digit numbers starting with digit 31 will be = 5 × 5 × 5 = 125 Number of 5 digit numbers starting with digit 32 will be = 5 × 5 &