the number of positive integers n in the range 12 ≤ n ≤ 40 such that the product ( n − 1 ) ( n − 2 ) . . . 3 . 2.1 is not divisible by n is
explanation : ( n - 1 ) ! is always divisible by n unless and untill n is a prime number e . g . ( 5 - 1 ) ! = 4 ! which is not divisible by 5 bcuz 5 is a prime number therefore , find all prime numbers in the range of 12 to 40 i . e 13 , 17 , 19 , 23 , 29 , 31 and 37 hence , the number of positive integers n is 7 . answer : b
add(add(3, 2), 2)