Question 266012
This word problem is on combinations..
How many ways can a student select five questions from an exam containing nine questions?
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9 choose 5
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The combinations of 9 things taken 5 at a time
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{{{9!/(5!(9-5)!)=362880/((120)(24))=362880/2880=126}}}
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How many ways are there if he must answer the first question and the last question? 
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Then there is no choice for 2 of the 5, so the only selections which
can be made for the remaining 3 are from the remaining 7. So it's
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7 choose 3
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the combinations of 7 things taken 3 at a time:
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{{{7!/(3!(7-3)!)=5040/((6)(24))=5040/144=35}}}
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Edwin