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gwd-9-24

Q24:

A certain fruit stand sold apples for $0.70 each and bananas for $0.50 each. If a customer

purchased both apples and bananas from the stand for a total of $6.30, what total number

of apples and bananas did the customer purchase?

A. 10

B. 11

C. 12

D. 13

E. 14

已经晕了,不是买9个苹果就6.3块了么?7只有乘以9后个位才会是3,苹果和香蕉一起买怎么也买不出6.3块啊?

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0.7*4+0.5*7=6.3
把所有的困苦都看做是有意义的,是生命对你的磨练,也许,是为了让你成大事而做准备。

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我拼出来是4个苹果+7个香蕉=4*0.7+7*0.5=6.3

但是答案不是11啊,不懂!

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apple(0.7) banana(0.5) banana(0.5)Apple
1x0.7 5.6/0.5=I , no 1x0.5 5.8/0.7, no
2x0.7 4.9/0.5=I, no 2x0.5 5.3/0.7, no
3x0.7 4.2/0.5, no 3x0.5 4.8/0.7, no
4x0.7 3.5/0.5, yes 4x0.5 4.3/0.7, no
5x0.7 2.8/0.5, no 5x0.5 3.8/0.7, no
6x0.7 2.1/0.5, no 6x0.5 3.3/0.7, no
7x0.7 1.4/0.5, no 7x0.5 2.8/0.7, yes
8x0.7 0.7/0.5, no 8x0.5 2.3/0.7, no
9x0.7 yes, 9x0.5 1.8/0.7,no
10x0.5 1.3/0.7, no
11x0.5 0.8/0.7, no
So, 11 is the only possible answer.

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0.7x+0.5y=0.63 =>x=(0.63-0.5y)/0.7=9-(5y)/7 => y=7, x=4.

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