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标题: GWD6-30 [打印本页]

作者: qiuqiaomm 时间: 2006-10-15 19:09 标题: GWD6-30

Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?

(1) She bought $4.40 worth of stamps.

(2) She bought an equal number of $0.15 stamps and $0.29 stamps.

Answer: A

My Answer: C

Did I miss something here? The question looks too simple... Pls help!

作者: robert 时间: 2006-10-15 22:40

请注意，邮票的张数必然是个整数。

作者: WalkByFaith 时间: 2006-10-17 11:01

QUOTE:

以下是引用robert在2006-10-15 22:40:00的发言：
请注意，邮票的张数必然是个整数。

嗯，这个很关键

作者: mereiful 时间: 2006-10-18 19:57

15x + 29y = 440

x >= 0, y >= 0且为整数，所以y必定能被5整除,
y = 5, 10, 15
很容易算出y=10,x=10是唯一解

作者: jiaminzhi 时间: 2006-10-21 20:01

The only thing you missed out is that the number of the $0.15 stamps and that of the $0.29 stamps must be integers.

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