No of 5 digit numbers starting with digit 1 =5×5×5×5=625 No of 5 digit numbers starting with digit 2 =5×5×5×5=625 No of 5 digit numbers starting with 31 =5×5×5=125 No of 5 digit numbers starting with 32 =5×5×5=125 No of 5 digit numbers starting with 33 =5×5×5=125 No of 5 digit numbers starting with 351 =5×5=25 No of 5 digit numbers starting with 352 =5×5=25 No of 5 digit numbers starting with 3531 =5 No of 5 digit numbers starting with 3532 =5 Before 35337 will be 4 numbers, So rank of 35337 will be 1690 So, in descending order serial number will be 3125−1690+1=1436