Jee mains pyq maths

Question

Let S = {1, 2, 3, 5, 7, 10, 11}. The number of nonempty subsets of S that have the sum of all elements a multiple of 3, is ___

Answer 1

Elements of the type 3k = 3 

Elements of the type 3k + 1 = 1, 7, 10 

Elements of the type 3k + 2 = 2, 5, 11 

Subsets containing one element S₁ = 1 

Subsets containing two elements