Question

the mean of a set of seven numbers is exactly 81. If one number is discarded, the average is exactly 78.Which number was discarded. 1)89 2)92 3)97 4)99 tell me how to do this?

Answer 1

you can try trial and error

Answer 2

or we can say this:

call x the number that we take out or discard: then simply we have:


7(81)-x=6(78)

Answer 3

Oh ight ill try that. thanks

Answer 4

solve for x


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Answer 5

it doesnt work?

Answer 6

nevr mind

Answer 7

it should work,
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Answer 8

i did a calculation mistake

Answer 9

oh okay\[\widetilde{aaa}\]