2024 AMC 8 第 12 题

Question

Rohan 在

4

个鱼缸中共养了

90

条孔雀鱼。

• 第

2

个鱼缸比第

1

个多

1

条孔雀鱼。

• 第

3

个鱼缸比第

2

个多

2

条孔雀鱼。

• 第

4

个鱼缸比第

3

个多

3

条孔雀鱼。

第

4

个鱼缸中有多少条孔雀鱼？

Rohan keeps a total of

90

guppies in

4

fish tanks.

• There is

1

more guppy in the

2

nd tank than in the

1

st tank.

• There are

2

more guppies in the

3

rd tank than in the

2

nd tank.

• There are

3

more guppies in the

4

th tank than in the

3

rd tank.

How many guppies are in the

4

th tank?

20

21

23

24

26

答案：E

知识点：一次方程

难度评级：980

小提示：

用第一个鱼缸的数量表示每个鱼缸

Write each tank amount in terms of the first tank

大提示：

第四个鱼缸比第一个多

6

条

The fourth tank has

6

more guppies than the first

视频讲解：

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文字解答：

设第

1

个鱼缸有

x

条孔雀鱼，则第

2

个鱼缸有

x+1

条，第

3

个鱼缸有

x+3

条，第

4

个鱼缸有

x+6

条。由

4

个鱼缸共有

90

条孔雀鱼求

x

：

x + x + 1 + x + 3 + x + 6 = 90

4x+10=90

x=20\text{。}

题目问的是第

4

个鱼缸的数量，不是第

1

个鱼缸。因此第

4

个鱼缸有

x+6=20+6=26

条。

正确答案是 E。

Let

x

be the number of guppies in the

1

st tank. Hence, there are

x+1

guppies in the

2

nd tank,

x+3

guppies in the

3

rd tank, and

x+6

guppies in the

4

th tank. We then use the fact that there are a total of

90

guppies in the

4

tanks to find

x

:

x + x + 1 + x + 3 + x + 6 = 90

4x+10=90

x=20.

Note that we are not yet done since we are asked for the number of guppies in the $4$ th tank and not the

1

st. There are

x+6=20+6=26

guppies in the

4

th tank.

Thus, E is the correct answer.

2024 AMC 8 第 12 题

答案：E

难度评级：980

小提示：

大提示：

视频讲解：

文字解答：

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