Let A = {1, 2, 3, 4, 5} and B = {6, 7}. What is the number of onto functions from A to B?
A.10
B.20
C.30✓ Correct
D.32
Explanation
Total functions from A (5 elements) to B (2 elements) = 2⁵ = 32. Non-onto functions are those mapping all elements to either 6 only or 7 only, which is 2 functions. Onto functions = 32 – 2 = 30.
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