Question

How many ways are there to choose a committee of 7 people from a group of 10 people?7201208405040?

Answer 1

Answer: 120

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Explanation:

We have seven slots to fill. Let's call the slots A, B, C, D, E, F, G

There are 10 choices for slot A

There are 9 choices for slot B

There are 8 choices for slot C

There are 7 choices for slot D

There are 6 choices for slot E

There are 5 choices for slot F

There are 4 choices for slot G

We count down because each previous slot reduces the pool to choose from. Multiply those values out: 10*9*8*7*6*5*4 = 604800

Now divide that result by 5040. Why 5040? Because this is the number of ways to arrange 7 people within a single grouping. Note how 7! = 7*6*5*4*3*2*1 = 5040. W're dividing because order does not matter for any committee.

So we have 604800/5040 = 120 which is the answer we want

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Side note: We could use the alternate route of the nCr combination formula

nCr = (n!)/(r!*(n-r)!)

where n = 10 and r = 7