Let = {1, 2, 3, ….., 40} and let A be a subset of such that no two elements in A have their sum divisible by 5. What is the maximum number of elements possible in A ?
(A) 10
(B) 13
(C) 17
(D) 20
Correct option (C) 17 Explanation:
A {1, 2,6,7,11,12,16,17, 21,22, 26,27,31,32,36,37} = & One of the element which is multiple of 5 B {3, 4,8,9,13,14,18,19,23, 24,28,29,33,34,38,39} = & One of the element which is multiple of 5.
