PREP题 貌似还没人提过 急 关于买票

rachel9

each person attending a fund-raising party for a certain club was charged the same admission fee. How many people attended the party?

(1)if the admission fee had been $0.75 less and 100 more people had attended, the club would have received the same amount in admission fees.

(2)if the admission fee had been $1.50 more and 100 fewer people had attended, the club would have received the same amount in admission fees.

答案是c

可是我算不出来……

谢谢……

mymengming

能算出来，n=300，p=3

rosemary99

麻烦楼上给个过程，谢谢

[此贴子已经被作者于2008-7-3 8:24:22编辑过]

seren_q

我没有算，只列了个等式：

Based on condition A: P*N=(P-0.75)*(N+100)

Based on condition B: P*N=(P+1.5)*(N-100)

You need both equations to caculate the value of P and N, so it must be C

rachel9

上面的等式始终有两个未知数，不知斑竹是怎么解出来的？

maomm

这题我也做错过,后来解决了.

(X-0.75)(Y+100) = XY

(X+1.5)(Y-100)= XY

=====XY+100X-0.75Y-75=XY

     XY-100X+1.5Y-150=XY

上两式相抵掉XY,100X-0.75Y=75

              100X-1.5Y=-150

希望能帮到你.

rachel9

这个结果不唯一阿！ 可以x=3 y=300 也可以x=6 y=500 以此类推还应该有不同的组合

seren_q

不会啊，x=6，y=500带入验算是不对的。其实这个题解起来还是很容易的

rachel9

我将x=6，y=500带入 100X-1.5Y=-150，也成立啊！这是怎么一回事啊？

magicbaby

...我只想说mm你算错了...

有两个方程，当然要两个都符合才行

建议把陈向东数学好好看看