Maths 丫~urgent~~

A每天可完成工程的 1/20
B每天可完成工程的 1/60

現假設 A、B工程隊共用了 X日完成工作，
當中 A休息了4日，B休息了 16日。

所以，　(X-4)*1/20 + (X-16)*1/60 = 1
　　　　　(X-4)*3 + (X-16) = 60
　　　　　3X - 12 + X - 16 = 60
　　　　　　　　　　4X = 88
　　　　　　　　　　X = 22
由於 A隊休息了4日，所以實際工作 22-4 = 18日

The rate of completion by A is 1/20 per day.
The rate of completion by B is 1/60 per day.

Now that,
A did 4 days => 4/20 = 1/5 completed.
B did another 16 days => 16/60 = 4/15 completed.

The portion not yet completed was 1 - 1/5 - 4/15 = 8/15.

If this is to be done by A, then
(8/15)/(1/20) = (20*8)/(15*1) = 160/15 = 10.67

Therefore, A has to do extra 11 days. (to integer days)

Notes:
1. A did 11 + 4 = 15 days on total.
2. If this is an IQ test, then A did 4 days (as specified by the question itself).

24日?!

2007-01-14 18:20:55 補充：
係關於邊課嫁..?