作者gcat (夏天！)
看板GRE
標題[計量] Magoosh數學請益
時間Fri Oct 11 15:34:28 2013
想問一下Magoosh數學裡面的一題，
Machine A can make 3 nails in 2 seconds. Working together, machines A and B
can make 10 nails in 3 seconds. How many seconds does it take machine B to
make 33 nails?
答案是18，但還是不懂怎麼解的?
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1F：推 branda0423 :VA(velocityA=1.5/sec),VB假設=X, 先由(1.5+X)3=10算 10/11 15:47
2F：→ branda0423 :出X,妳有VB就能算要多久啦 10/11 15:47
3F：推 bear62479 :先算出A的效率 = 3/2 nails per s, 再假設b效率為y 10/11 15:48
4F：→ bear62479 :最後AB合作效率帶進去解10N/3S就可以解出來了 10/11 15:48
5F：推 kerotama :B每秒5.5/3 故33/(5.5/3) = 18 10/11 15:53
6F：推 Ghamu :A:3n/2s A+B:10n/3s => A:9n/6s A+B:20n/6s 10/11 16:11
7F：→ Ghamu :=> B:11n/6s =>33n/18s Ans:18sec 10/11 16:12
8F：→ gcat :原來是用效率的觀念~大感謝~ 10/13 20:32