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标题: 求助KALPLAN一道数学题 [打印本页]

作者: Chowmeiner 时间: 2008-9-22 07:17 标题: 求助KALPLAN一道数学题

求助KALPLAN一道数学题

A customer using a certain telephone calling plan pays a fee of $25 per month, and then receives a discount of 40% on the regular charge for all calls made to Country A. If calls to Country A are regularly charged at $1.60 per minute for the first 3 minutes, and $0.80 per minute for each minute thereafter, what is the maximum the customer could have saved over regular prices if he was charged for 1 hour of calls made to Country A in a certain month?

A. 8.75 B 12 C 13.4 .D 17.4 E 24.4

Key: A.

My solution:

(1.6*3+0.8*57)*0.4=20.16

应该怎么做啊？

作者: greatvampirer 时间: 2008-9-23 06:45

答案错了，应该是13.4

什么情况下最贵？就是每次正好打3分钟，这样一小时就是1.6x60=96

这被打了六折，也就是57.6，这样他就省了38.4

但是他要为此付出25块的租金，所以和不加入相比，他省了13.4

作者: greatvampirer 时间: 2008-9-23 20:16

这些条件，怎么算都不可能和0.75扯上关系啊!

作者: Chowmeiner 时间: 2008-9-24 19:42

Thanks ! Certainly many people are "bi ni sha", including me.

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