# combinations problem

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• Feb 3rd 2009, 11:22 AM
halb
combinations problem
seven managers and eight sales representatives volunteer to attend a trade show, their company can afford to send five people, in how many ways could they by selected

if there must be at least one manager and one sales representative chosen?
• Feb 3rd 2009, 11:59 AM
Plato
Quote:

Originally Posted by halb
seven managers and eight sales representatives volunteer to attend a trade show, their company can afford to send five people, in how many ways could they by selected if there must be at least one manager and one sales representative chosen?

\$\displaystyle {15 \choose 5}-{8 \choose 5}-{7 \choose 5}\$

Now please reply, explaning why that is the correct answer.
• Feb 3rd 2009, 01:21 PM
halb
it is the correct answer, that was what was in the back of the book
• Feb 3rd 2009, 02:10 PM
Plato
Quote:

Originally Posted by halb
it is the correct answer, that was what was in the back of the book

Is that the way you explain why a particular number is correct?
Really? Because the back of the book says so?