SOLUTION: A manager wants to assign 20 workers to four distinct construction jobs. These jobs require 6, 4, 3, and 7 workers respectively. In how many different ways can the manager assign t

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Question 1114944: A manager wants to assign 20 workers to four distinct construction jobs. These jobs require 6, 4, 3, and 7 workers respectively. In how many different ways can the manager assign the workers?

Found 2 solutions by math_helper, greenestamps:
Answer by math_helper(2461) About Me  (Show Source):
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I think it would be 20C6 * 14C4 * 10C3 * 7C7 = +highlight%28+4655851200+%29++ ways.

It seems arbitrary to assign the group of 6 workers first, but this result is independent of which group you assign first. Even if you group, say, the 7 workers first for their job, the result is the same:
20C7 * 13C6 * 7C4 * 3C3 = +highlight+%28+4655851200+%29+ ways.

Of course, more complex assignments are possible (assign job 1 to a person from group of 6, assign job 2 to a person from the group of 3, etc.), but the number of possible ways should still be the same.

Answer by greenestamps(13198) About Me  (Show Source):
You can put this solution on YOUR website!


The number is the coefficient of the %28a%5E6%29%28b%5E4%29%28c%5E3%29%28d%5E7%29 term in the expansion of %28a%2Bb%2Bc%2Bd%29%5E20.

That number is the multinomial coefficient (20;6,4,3,7) (my notation) which is calculated as

%2820%21%29%2F%28%286%21%29%284%21%29%283%21%29%287%21%29%29+=+4655851200

So the method used by the other tutor is also valid.