If A = {1,2,3,4,5}, how many members of P(A) have an even sum of elements?
Answer and explanation
Correct answer: 16
There are 2^5 = 32 subsets in P(A). Pair every subset S with S △ {1}, where 1 is odd; toggling 1 changes the parity of the subset sum. Thus each pair contains one even-sum subset and one odd-sum subset. Consequently the 32 subsets divide equally, and the number with an even sum is 32/2 = 16.
Frequently asked questions
What is the correct answer to this question?
16
Why is this the correct answer?
There are 2^5 = 32 subsets in P(A). Pair every subset S with S △ {1}, where 1 is odd; toggling 1 changes the parity of the subset sum. Thus each pair contains one even-sum subset and one odd-sum subset. Consequently the 32 subsets divide equally, and the number with an even sum is 32/2 = 16.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Sets. Topic: Power Set and Subsets.