[問題]GWD 13-20

[luluhsiao]

Q20:
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?

Ans : B. 1/6


麻煩一下大家了...謝謝

[homaru]

設另外20個數總和為T
n=4*T/20=T/5
the sum of the 21 numbers =T + T/5=6T/5
n占全部總和的比例=(T/5)/(6T/5)=1/6

建議你貼題目時
把全部選項都貼出來才完整喔~
感謝

[luluhsiao]

OK!!謝謝你啦....

[SELVICHY]

[quote="luluhsiao"]Q20:
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?

Ans : B. 1/6


麻煩一下大家了...謝謝[/quote]

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更快的算法
設20個數字的平均為X,則n=4x, 21個數的總合為24x
4x/24x=1/6