2017 AMC 10B 第 5 题

Question

Camilla 原来拥有的蓝莓味软糖数量是樱桃味软糖数量的两倍。她每种各吃了

10

颗后，蓝莓味软糖数量变成樱桃味软糖数量的三倍。她原来有多少颗蓝莓味软糖？

Camilla had twice as many blueberry jelly beans as cherry jelly beans. After eating

10

pieces of each kind, she now has three times as many blueberry jelly beans as cherry jelly beans. How many blueberry jelly beans did she originally have?

10

20

30

40

50

答案：D

知识点：方程组一次方程

难度评级：900

小提示：

设原来的樱桃味和蓝莓味软糖数量为变量。

Let the original cherry and blueberry counts be variables

大提示：

用吃之前和吃之后的两个关系式。

Use one equation before and one equation after eating the jelly beans

解答：

设原来樱桃味有

c

颗，蓝莓味有

b

颗。

由第一句和第二句分别可得

b = 2c

b-10=3(c-10)

这两个方程。

因此

2c-10 = 3c-30

c=20\text{。}

这说明

b = 2\cdot 20=40\text{。}

所以正确答案是 D。

Let the number of cherry jelly beans be

c

and let the number of blueberry jelly beans be

b.

Then, we know

b = 2c

b-10=3(c-10)

from the first and second statements respectively.

Therefore,

2c-10 = 3c-30

c=20.

This means that

b = 2\cdot 20=40.

Thus, the correct answer is D .

2017 AMC 10B 第 5 题

答案：D

难度评级：900

小提示：

大提示：

解答：

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