by using the numbers 1 , 2 , 3 , 7 and 9 only once , how many 5 digit numbers can be made that are divisible by 25 ?
a number to be divisible by 25 must end with 00 , 25 , 50 , or 75 . so , not possible . answer : c .
add(add(const_3, const_2), 1)