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 ✓
- D. 32
Correct Answer: C. 30
Explanation
The total number of functions from set A to set B is 2^5 = 32. Functions that are NOT onto map all elements of A to exactly one element of B (either all to 6 or all to 7), which gives 2 such functions. The number of onto functions is 32 - 2 = 30.
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