[求助] TTGWD 9-17

oneseven · 发表于 2007-8-26 01:25:00

Q17:

A certain list consists of 21 different numbers. If n is in the list and n is 4 times the average (arithmetic mean) of the other 20 numbers in the list, then n is what fraction of the sum of the 21 numbers in the list?

A. 1/20

B. 1/6

C. 1/5

D. 4/21

E. 5/21

shelly97209 · 发表于 2007-8-26 02:29:00

B.
let the average of the 20 numbers be X
4X / (20X+4X) = 1/6
hope that helps

allenhzkk · 发表于 2007-8-26 02:50:00

太厉害了，这么简单

[此贴子已经被作者于2007-8-26 2:52:50编辑过]

[求助] TTGWD 9-17

[求助] TTGWD 9-17

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