[問題]天山03-17

[cafe]

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

答案B,不知道那跟筋不對,都算不出來正確答案,希望大家幫幫忙

[JS]

presume the average mean of the 20 munbers is x
the sum of that 20 number is then 20x
and n is 4x

4x / 20x+4x =1/6

[micht]

謝謝JS熱心幫大家解題唷;heart

[cafe]

presume the average mean of the 20 munbers is x
the sum of that 20 number is then 20x
and n is 4x

4x / 20x+4x =1/6

I know what mistake I made...Thank you:)