how many 4 - digit numerals begin with a digit that represents a prime and end with a digit that represents a prime number ?
"prime digits 2 , 3,5 and 7 . three digit numbers _ _ _ 1 st place can be filled in 4 ways 2 nd place can be filled in 10 ways 3 rd place can be filled in 10 ways 3 rd place can be filled in 4 ways total = 4 * 10 * 10 * 4 = 1600 ans : a"
add(multiply(const_100, 4), const_100)