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Up4
A teacher wants to select groups of 3 students out of 15 for a group work. How many different groups of 3 are possible?
- A. 455
- B. 45
- C. 225
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Up2
The correct answer is A.
Counting problems involve determining the exact number of ways two or more operations or events can be performed together. This particular counting problem can be solved using a combination, which is basically a selection of some given items where the order does not matter. The formula is:
nCr = n!/((n-r)!r!)
Where
n=15; and
r=3nCr = 15!/((15-3)!*3!) = 455
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