2010 AMC 10A 第 3 题

Question

Tyrone 有

97

颗弹珠，Eric 有

11

颗弹珠。之后 Tyrone 给了 Eric 一些弹珠，使得最后 Tyrone 的弹珠数是 Eric 的两倍。Tyrone 给了 Eric 多少颗弹珠？

Tyrone had

97

marbles and Eric had

11

marbles. Tyrone then gave some of his marbles to Eric so that Tyrone ended with twice as many marbles as Eric. How many marbles did Tyrone give to Eric?

3

13

18

25

29

答案：D

知识点：一次方程比与比例

难度评级：960

小提示：

弹珠总数保持不变。

The total number of marbles stays fixed

大提示：

最后的数量比为

2:1

。

The final amounts are in the ratio

2:1

解答：

设 Eric 最后有

x

颗弹珠，则 Tyrone 最后有

2x

颗。

总弹珠数为

97 + 11 = 108

，所以

3x = 108

x = 36\text{。}

因此 Tyrone 最后有

36 \cdot 2 = 72

颗弹珠，他给出了

97 - 72 = 25

颗。

所以正确答案是 D。

Let

x

be the number of marbles that Eric ends up with. Then Tyrone ends up with

2x.

The total number of marbles is

97 + 11 = 108,

so

3x = 108

x = 36.

Then, Tyrone ends up with

36 \cdot 2 = 72

marbles. This means he has to give away

97 - 72 = 25

marbles.

Thus, D is the correct answer.

2010 AMC 10A 第 3 题

答案：D

难度评级：960

小提示：

大提示：

解答：

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