2003 AMC 8 真题

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1.

Jamie 数了一个立方体的棱数,Jimmy 数了顶点数,Judy 数了面数。然后他们把这三个数相加。得到的和是多少?

Jamie counted the number of edges of a cube, Jimmy counted the numbers of corners, and Judy counted the number of faces. They then added the three numbers. What was the resulting sum?

1212

1616

2020

2222

2626

答案:E
知识点:正方体

难度评级:370

解答:

一个立方体有 1212 条棱、88 个顶点和 66 个面。相加得到 12+8+6=26. 12 + 8 + 6 = 26.

所以正确答案是 E

A cube has 1212 edges, 88 corners, and 66 faces. Adding these together yields 12+8+6=26. 12 + 8 + 6 = 26.

Thus, E is the correct answer.

2.

下列哪个数的最小质因数最小?

Which of the following numbers has the smallest prime factor?

5555

5757

5858

5959

6161

答案:C
知识点:质数奇偶性

难度评级:450

解答:

最小的质数是 22。因此任何偶数都会是答案。

所以正确答案是 C

Note that the smallest prime number is 2.2. This means that any even number would be our answer.

Thus, C is the correct answer.

3.

Ricky C's 的一个汉堡重 120120 克,其中 3030 克是填充物。汉堡中不是填充物的部分占百分之多少?

A burger at Ricky C's weighs 120120 grams, of which 3030 grams are filler. What percent of the burger is not filler?

60%60 \%

65%65 \%

70%70 \%

75%75 \%

90%90 \%

答案:D
知识点:百分数

难度评级:560

解答:

不是填充物的部分为 12030=90120 - 30 = 90 克。因此百分比为 10090120=10034=75%. 100 \cdot \dfrac{90}{120} = 100 \cdot \dfrac{3}{4} = 75 \%.

所以正确答案是 D

We get that 12030=90120 - 30 = 90 grams are not filler. The percentage is therefore 10090120=10034=75%. 100 \cdot \dfrac{90}{120} = 100 \cdot \dfrac{3}{4} = 75 \%.

Thus, D is the correct answer.

4.

一群骑自行车和三轮车的孩子经过 Billy Bob 家。Billy Bob 数到 77 个孩子和 1919 个轮子。有多少辆三轮车?

A group of children riding on bicycles and tricycles rode past Billy Bob's house. Billy Bob counted 77 children and 1919 wheels. How many tricycles were there?

22

44

55

66

77

答案:C
知识点:方程组

难度评级:720

解答:

bb 为自行车数量,tt 为三轮车数量。可列方程组 b+t=7,2b+3t=19. \begin{gather*} b + t = 7, \\ 2b + 3t = 19. \end{gather*} 将第一个方程乘以 22,再从第二个方程中相减,得到 t=5t = 5

所以正确答案是 C

Let bb be the number of bicycles and tt be the number of tricycles. Then we can set up the following system of equations: b+t=7,2b+3t=19. \begin{gather*} b + t = 7, \\ 2b + 3t = 19. \end{gather*} Multiplying the first equation by 22 and subtracting from the second equation, we get t=5.t = 5.

Thus, C is the correct answer.

5.

如果一个数的 20%20 \%1212,那么同一个数的 30%30\% 是多少?

If 20%20 \% of a number is 12,12, what is 30%30\% of the same number?

1515

1818

2020

2424

3030

答案:B
知识点:百分数

难度评级:730

解答:

因为这个数的 20%20\%1212,所以这个数的 10%10\%66

因此同一个数的 30%30\%36=183\cdot6=18

所以正确答案是 B

Since 20%20\% of the number is 1212, 10%10\% of the number is 66.

Therefore 30%30\% of the same number is 36=183\cdot6=18.

Thus, B is the correct answer.

6.

根据图中三个正方形的面积,内部三角形的面积是多少?

Given the areas of the three squares in the figure, what is the area of the interior triangle?

1313

3030

6060

300300

18001800

答案:B

难度评级:920

解答:

三个正方形的边长分别为 169=13 \sqrt{169} = 13 144=12, \sqrt{144} = 12, 25=5. \sqrt{25} = 5. 这些长度构成一个勾股数组。

因此内部三角形是直角三角形,面积为 12512=30. \dfrac{1}{2} \cdot 5 \cdot 12 = 30.

所以正确答案是 B

We get that the side lengths of the squares are 169=13 \sqrt{169} = 13144=12, \sqrt{144} = 12, 25=5. \sqrt{25} = 5. respectively. Note that these lengths form a Pythagorean triple.

Therefore, the interior triangle is right. Its area is 12512=30. \dfrac{1}{2} \cdot 5 \cdot 12 = 30.

Thus, B is the correct answer.

7.

Blake 和 Jenny 各参加了四次 100100 分测试。Blake 四次测试平均分为 7878。Jenny 第一次测试比 Blake 高 1010 分,第二次比他低 1010 分,第三次和第四次都比他高 2020 分。Jenny 的平均分和 Blake 的平均分相差多少?

Blake and Jenny each took four 100100-point tests. Blake averaged 7878 on the four tests. Jenny scored 1010 points higher than Blake on the first test, 1010 points lower than him on the second test, and 2020 points higher on both the third and fourth tests. What is the difference between Jenny's average and Blake's average on these four tests?

1010

1515

2020

2525

4040

答案:A
知识点:平均数

难度评级:900

解答:

两人四次测试的总分差为 1010+202=40. 10 - 10 + 20 \cdot 2 = 40. 平均分差为 40÷4=10.40 \div 4 = 10.

所以正确答案是 A

The total point difference between the two is 1010+202=40. 10 - 10 + 20 \cdot 2 = 40. The average of this difference is 40÷4=10.40 \div 4 = 10.

Thus, A is the correct answer.

8.

8,9,8, 9,1010 题使用随附段落和图形中的数据。

烘焙义卖

四个朋友 Art、Roger、Paul 和 Trisha 烤饼干,所有饼干厚度相同。饼干的形状如下所示。

• Art 的饼干是梯形:

• Roger 的饼干是长方形:

• Paul 的饼干是平行四边形:

• Trisha 的饼干是三角形:

每个朋友使用相同数量的面团,且 Art 正好做了 1212 块饼干。

谁用一批饼干面团做出的饼干数量最少?

Problems 8,9,8, 9, and 1010 use the data found in the accompanying paragraph and figures.

Bake Sale

Four friends, Art, Roger, Paul and Trisha, bake cookies, and all cookies have the same thickness. The shapes of the cookies differ, as shown.

• Art's cookies are trapezoids:

• Roger's cookies are rectangles:

• Paul's cookies are parallelograms:

• Trisha's cookies are triangles:

Each friend uses the same amount of dough, and Art makes exactly 1212 cookies.

Who gets the fewest cookies from one batch of cookie dough?

Art\text{Art}

Paul\text{Paul}

Roger\text{Roger}

Trisha\text{Trisha}

最少数量出现并列

There is a tie for fewest.

答案:A
知识点:面积最优化

难度评级:1000

解答:

因为所有饼干厚度相同且使用相同数量的面团,所以面积最大的饼干形状会产生最少的饼干。

Art 的梯形面积为 12(3+5)3=12\frac12(3+5)\cdot3=12。Roger 的长方形面积为 42=84\cdot2=8。Paul 的平行四边形面积为 32=63\cdot2=6,Trisha 的三角形面积为 1234=6\frac12\cdot3\cdot4=6

Art 的饼干面积最大,所以 Art 用一批面团得到的饼干最少。

所以正确答案是 A

Since the cookies all have the same thickness and use the same amount of dough, the largest cookie shape produces the fewest cookies.

Art’s trapezoid has area 12(3+5)3=12\frac12(3+5)\cdot3=12. Roger’s rectangle has area 42=84\cdot2=8. Paul’s parallelogram has area 32=63\cdot2=6, and Trisha’s triangle has area 1234=6\frac12\cdot3\cdot4=6.

Art has the largest cookie area, so Art gets the fewest cookies from one batch.

Thus, A is the correct answer.

9.

Art 的饼干每块卖 6060¢。为了从一批面团中赚到同样金额,Roger 的一块饼干应卖多少钱?

Art's cookies sell for 6060¢ each. To earn the same amount from a single batch, how much should one of Roger's cookies cost?

1818¢

2525¢

4040¢

7575¢

9090¢

答案:C
知识点:面积比与比例

难度评级:1060

解答:

Art 做 1212 块饼干,每块卖 6060 分,所以一批收入 1260=72012\cdot60=720 分。

这批面团面积为 1212=14412\cdot12=144 平方英寸,每块 Roger 饼干面积为 42=84\cdot2=8。因此 Roger 能做 144÷8=18144\div8=18 块饼干。

若要用 1818 块饼干赚 720720 分,每块 Roger 饼干应卖 720÷18=40720\div18=40 分。

所以正确答案是 C

Art makes 1212 cookies that sell for 6060 cents each, so one batch earns 1260=72012\cdot60=720 cents.

The batch has 1212=14412\cdot12=144 square inches of dough area, and each Roger cookie has area 42=84\cdot2=8. Thus Roger makes 144÷8=18144\div8=18 cookies.

To earn 720720 cents from 1818 cookies, each Roger cookie should cost 720÷18=40720\div18=40 cents.

Thus, C is the correct answer.

10.

一批 Trisha 的饼干会有多少块?

How many cookies will be in one batch of Trisha's cookies?

1010

1212

1616

1818

2424

答案:E
知识点:面积比与比例

难度评级:1030

解答:

Art 的一块饼干面积为 1212 平方英寸,所以整批面团面积为 1212=14412\cdot12=144 平方英寸。

Trisha 的三角形饼干面积为 1234=6\frac12\cdot3\cdot4=6 平方英寸。

因此 Trisha 每批可以做 144÷6=24144\div6=24 块饼干。

所以正确答案是 E

Art’s cookie area is 1212 square inches, so the whole batch has area 1212=14412\cdot12=144 square inches.

Trisha’s triangular cookie has area 1234=6\frac12\cdot3\cdot4=6 square inches.

Therefore Trisha can make 144÷6=24144\div6=24 cookies per batch.

Thus, E is the correct answer.

11.

Lou's Fine Shoes 生意有点慢,于是 Lou 决定促销。星期五,Lou 将星期四所有价格提高 10%10 \%。周末,Lou 做广告:“标价九折,促销星期一开始。”星期四售价 $40\$40 的一双鞋,星期一卖多少钱?

Business is a little slow at Lou's Fine Shoes, so Lou decides to have a sale. On Friday, Lou increases all of Thursday's prices by 10%.10 \%. Over the weekend, Lou advertises the sale: "Ten percent off the listed price. Sale starts Monday." How much does a pair of shoes cost on Monday that cost $40\$40 on Thursday?

$36\$36

$39.60\$39.60

$40\$40

$40.40\$40.40

$44\$44

答案:B
知识点:百分数

难度评级:1060

解答:

星期五鞋价提高 10%10\%,所以标价变为 401.10=4440\cdot1.10=44 美元。

星期一再打 10%10\% 的折扣,从 $44\$44 降到 440.90=39.6044\cdot0.90=39.60 美元。

所以正确答案是 B

On Friday, the shoes are marked up by 10%10\%, so the listed price becomes 401.10=4440\cdot1.10=44 dollars.

On Monday, the 10%10\% discount is taken from $44\$44, giving 440.90=39.6044\cdot0.90=39.60 dollars.

Thus, B is the correct answer.

12.

当一个公平的六面骰子被掷到桌面上时,底面看不见。可见的五个面上的数字乘积能被 66 整除的概率是多少?

When a fair six-sided die is tossed on a table top, the bottom face cannot be seen. What is the probability that the product of the numbers on the five faces that can be seen is divisible by 66?

13\frac 13

12\frac 12

23\frac 23

56\frac 56

11

答案:E

难度评级:1120

解答:

如果数字 66 的面可见,那么可见数字的乘积能被 66 整除。

如果数字 66 在底面,那么可见面仍包含 2233,所以它们的乘积仍能被 66 整除。

每种可能的掷骰结果都满足条件,所以概率为 11

所以正确答案是 E

If the face numbered 66 is visible, then the visible product is divisible by 66.

If the face numbered 66 is on the bottom, then the visible faces include both 22 and 33, so their product is still divisible by 66.

Every possible toss works, so the probability is 11.

Thus, E is the correct answer.

13.

十四个白色立方体拼成右图。这个立体的整个表面,包括底面,都被涂色。然后将这个立体拆成单个立方体。有多少个单个立方体恰好有四个面被涂色?

Fourteen white cubes are put together to form the figure on the right. The complete surface of the figure, including the bottom, is painted. The figure is then separated into individual cubes. How many of the individual cubes have exactly four painted faces?

44

66

88

1010

1212

答案:B

难度评级:1240

解答:

一个小立方体恰好有四个面被涂色,当且仅当它恰好与两个其他立方体相连。

44 个顶部立方体只接触一个其他立方体,所以它们有 55 个涂色面。44 个底部角落立方体接触三个其他立方体,所以它们有 33 个涂色面。

剩下的 1444=614-4-4=6 个立方体各恰好接触两个其他立方体,所以它们恰好有四个涂色面。

所以正确答案是 B

A cube has exactly four painted faces exactly when it is attached to exactly two other cubes.

The 44 top cubes touch only one other cube, so they have 55 painted faces. The 44 bottom corner cubes touch three other cubes, so they have 33 painted faces.

The remaining 1444=614-4-4=6 cubes each touch exactly two other cubes, so they have exactly four painted faces.

Thus, B is the correct answer.

14.

在这个加法题中,每个字母代表一个不同数字。 TWO+TWOFOUR\begin{array}{cccc}&T & W & O\\ +&T & W & O\\ \hline F& O & U & R\end{array} 如果 T=7T = 7,且字母 OO 表示一个偶数,那么 WW 唯一可能的值是多少?

In this addition problem, each letter stands for a different digit. TWO+TWOFOUR\begin{array}{cccc}&T & W & O\\ +&T & W & O\\ \hline F& O & U & R\end{array} If T=7T = 7 and the letter OO represents an even number, what is the only possible value for W?W?

00

11

22

33

44

答案:D

难度评级:1380

解答:

因为两个 TT 都是 77,所以 OO4455。由于 OO 是偶数,得到 O=4O = 4

于是 R=4+4=8R = 4 + 4 = 8。还知道 W+WW + W 不会进位,否则 OO 会是 55

因此 WW 小于 55,且不能是 4411。如果 W=0W = 0,则 U=0U = 0,两个字母会代表同一个数字。如果 W=2W = 2,则 U=4U = 4,这也不允许。

所以 W=3W = 3

所以正确答案是 D

Since both TT's are 7,7, we get that OO is either 44 or 5.5. Since OO is even, we get that O=4.O = 4.

Then, we get that R=4+4=8.R = 4 + 4 = 8. We also know that W+WW + W doesn't carry over, since otherwise OO would be 5.5.

Therefore, WW is less than 55 and cannot be 44 or 1.1. If W=0,W = 0, then U=0,U = 0, which gives two letters the same digit. If W=2,W = 2, then U=4,U = 4, which is also not allowed.

This makes W=3.W = 3.

Thus, D is the correct answer.

15.

一个图形由单位立方体构成。每个立方体至少与另一个立方体共享一个面。若要得到图中所示的正视图和侧视图,最少需要多少个立方体?

A figure is constructed from unit cubes. Each cube shares at least one face with another cube. What is the minimum number of cubes needed to build a figure with the front and side views shown?

33

44

55

66

77

答案:B

难度评级:1330

解答:

正视图需要一个有三个可见位置的 L 形,所以至少需要三个立方体。

若只有三个立方体,它们都必须占据这三个正视图位置。这样侧视图只会有一个深度列,而不是所需的 L 形。

图中的四立方体构造具有两个所需视图,所以最小值是 44

所以正确答案是 B

The front view requires an L-shape with three visible positions, so at least three cubes are needed.

With only three cubes, all cubes would have to occupy those three front-view positions. Then the side view would have only one depth column, not the required L-shape.

The shown four-cube construction has both required views, so the minimum is 44.

Thus, B is the correct answer.

16.

Ali、Bonnie、Carlo 和 Dianna 将一起开车去附近的主题公园。他们使用的车有四个座位:一个驾驶座、一个前排乘客座和两个后排座位。只有 Bonnie 和 Carlo 会开这辆车。有多少种可能的座位安排?

Ali, Bonnie, Carlo and Dianna are going to drive together to a nearby theme park. The car they are using has four seats: one driver’s seat, one front passenger seat and two back seats. Bonnie and Carlo are the only two who can drive the car. How many possible seating arrangements are there?

22

44

66

1212

2424

答案:D

难度评级:1230

解答:

驾驶座有 22 种选择。另一个前排座位有 33 种选择,第一个后排座位有 22 种选择。

最后一个人必须坐最后一个座位,所以共有 232=12 2 \cdot 3 \cdot 2 = 12 种座位安排。

所以正确答案是 D

There are 22 options for who sits in the driver's seat. There are 33 options for the other front seat, and 22 options for the first back seat.

The last person has to sit in the last seat, for a total of 232=12 2 \cdot 3 \cdot 2 = 12 possible seating arrangements.

Thus, D is the correct answer.

17.

下面列出的六个孩子来自两个家庭,每个家庭有三个兄弟姐妹。每个孩子有蓝色或棕色眼睛,以及黑色或金色头发。同一个家庭的孩子至少有其中一个特征相同。哪两个孩子是 Jim 的兄弟姐妹?

The six children listed below are from two families of three siblings each. Each child has blue or brown eyes and black or blond hair. Children from the same family have at least one of these characteristics in common. Which two children are Jim's siblings?

Nadeen 和 Austin

Nadeen and Austin

Benjamin 和 Sue

Benjamin and Sue

Benjamin 和 Austin

Benjamin and Austin

Nadeen 和 Tevyn

Nadeen and Tevyn

Austin 和 Sue

Austin and Sue

答案:E
知识点:逻辑推理

难度评级:1380

解答:

Nadeen、Austin 和 Sue 是唯一与 Jim 共享某个特征的 33 个人。需要找出其中哪一个与其他人完全不同。

Austin 和 Sue 都有蓝色眼睛,所以 Nadeen 是不属于这一组的人。因此 Austin 和 Sue 是 Jim 的兄弟姐妹。

所以正确答案是 E

Note that Nadeen, Austin, and Sue are the only individuals who share a characteristic with Jim. We need to find which of the 33 are completely different from the others.

Austin and Sue both have blue eyes, which makes Nadeen the odd one out. Therefore, Austin and Sue are Jim's siblings.

Thus, E is the correct answer.

18.

下图中的二十个点各代表 Sarah 的一位同学。互为朋友的同学之间用线段连接。Sarah 生日聚会只邀请以下同学:她所有的朋友,以及至少和她某个朋友是朋友的同学。有多少位同学不会被邀请参加 Sarah 的聚会?

Each of the twenty dots on the graph below represents one of Sarah's classmates. Classmates who are friends are connected with a line segment. For her birthday party, Sarah is inviting only the following: all of her friends and all of those classmates who are friends with at least one of her friends. How many classmates will not be invited to Sarah's party?

11

44

55

66

77

答案:D
知识点:图论补集计数

难度评级:1400

解答:

Sarah 邀请她的朋友,以及至少和她某个朋友是朋友的同学。用图论语言说,她邀请距离 Sarah 为 1122 条线段的点。

从图中可见,有 44 个点与 Sarah 所在连通分量断开,另外还有 22 个点在 Sarah 所在连通分量中但距离为 33 条线段。

因此不会被邀请的同学有 4+2=64+2=6 位。

所以正确答案是 D

Sarah invites her friends and the classmates who are friends with at least one of her friends. In graph terms, she invites dots that are 11 or 22 line segments away from Sarah.

From the graph, 44 dots are disconnected from Sarah’s component, and 22 more dots in Sarah’s component are 33 segments away.

Those 4+2=64+2=6 classmates will not be invited.

Thus, D is the correct answer.

19.

1000100020002000 之间有多少个整数同时以 15,20,15, 20,2525 为因数?

How many integers between 10001000 and 20002000 have all three of the numbers 15,20,15, 20, and 2525 as factors?

11

22

33

44

55

答案:C

难度评级:1430

解答:

如果一个数 xx 以这三个数为因数,那么它们的最小公倍数也必须整除 xx

这些数的质因数分解为 15=35, 15 = 3 \cdot 5, 20=225, 20 = 2^2 \cdot 5, 25=52. 25 = 5^2.

因此最小公倍数为 22352=300. 2^2 \cdot 3 \cdot 5^2 = 300.

300300 的倍数中,位于 1000100020002000 之间的是 1200,1500,1200, 1500,18001800

所以正确答案是 C

If a number xx has these three numbers as factors, then their least common multiple must also divide x.x.

These numbers have the following prime factorizations: 15=35, 15 = 3 \cdot 5,20=225, 20 = 2^2 \cdot 5,25=52. 25 = 5^2.

From these values, we get that the least common multiple is 22352=300. 2^2 \cdot 3 \cdot 5^2 = 300.

Therefore, the multiples of 300300 between 10001000 and 20002000 are 1200,1500,1200, 1500, and 1800.1800.

Thus, C is the correct answer.

20.

凌晨 4:204:20 时,钟表两根指针形成的锐角是多少度?

What is the measure of the acute angle formed by the hands of a clock at 4:204:20 a.m.?

00^{\circ}

55^{\circ}

88^{\circ}

1010^{\circ}

1212^{\circ}

答案:D
知识点:时钟

难度评级:1450

解答:

4:204 : 20,时针位于 4455 之间 13\frac{1}{3} 的位置。

每个小时刻度代表 360÷12=30360 \div 12 = 30^{\circ}。所以时针从 44 之后又移动了 30÷3=1030 \div 3 = 10^{\circ}

注意 2020 分钟时,分针指向 44。因此形成的角为 1010^{\circ}

所以正确答案是 D

At 4:20,4 : 20, the hour hand will be a 13\frac{1}{3} of the way between 44 and 5.5.

Each hour represents 360÷12=30.360 \div 12 = 30^{\circ}. This means the hour hand will be 30÷3=1030 \div 3 = 10^{\circ} past 4.4.

Note that at 2020 minutes, the minute hand will be at 4.4. This means the degree formed is 10.10^{\circ}.

Thus, D is the correct answer.

21.

梯形 ABCDABCD 的面积是 164 cm2164\text{ cm}^2。高为 88 cm,ABAB1010 cm,CDCD1717 cm。BCBC 等于多少厘米?

The area of trapezoid ABCDABCD is 164 cm2.164\text{ cm}^2. The altitude is 88 cm, ABAB is 1010 cm, and CDCD is 1717 cm. What is BC,BC, in centimeters?

99

1010

1212

1515

2020

答案:B

难度评级:1590

解答:

BBCCAD\overline{AD} 作垂线,垂足分别为 EEFF

在左右两个直角三角形中,AE=10282=6AE=\sqrt{10^2-8^2}=6FD=17282=15FD=\sqrt{17^2-8^2}=15

两侧三角形面积分别为 1268=24\frac12\cdot6\cdot8=2412158=60\frac12\cdot15\cdot8=60。中间长方形面积为 8BC8\cdot BC

因此 164=24+60+8BC164=24+60+8BC,所以 8BC=808BC=80BC=10BC=10

所以正确答案是 B

Drop perpendiculars from BB and CC to AD\overline{AD}, meeting it at EE and FF.

In the left and right right triangles, AE=10282=6AE=\sqrt{10^2-8^2}=6 and FD=17282=15FD=\sqrt{17^2-8^2}=15.

The two side triangles have areas 1268=24\frac12\cdot6\cdot8=24 and 12158=60\frac12\cdot15\cdot8=60. The middle rectangle has area 8BC8\cdot BC.

Thus 164=24+60+8BC164=24+60+8BC, so 8BC=808BC=80 and BC=10BC=10.

Thus, B is the correct answer.

22.

下列图形由正方形和圆组成。哪个图形的阴影区域面积最大?

The following figures are composed of squares and circles. Which figure has a shaded region with largest area?

只有 AA

AA only

只有 BB

BB only

只有 CC

CC only

AABB 都是

both AA and BB

全部相等

all are equal

答案:C
知识点:圆面积面积

难度评级:1580

解答:

在图形 AA 中,阴影面积是一个 2222 正方形面积减去半径为 11 的圆面积,即 4π4-\pi

图形 BB 由四个图形 AA 的半尺寸副本组成,所以总阴影面积也为 4π4-\pi

在图形 CC 中,圆的半径为 11,内接正方形的对角线为 22,所以其面积为 22。阴影面积为 π2\pi-2

因为 π>3\pi>3,所以 π2>4π\pi-2>4-\pi,因此图形 CC 的阴影面积最大。

所以正确答案是 C

In figure AA, the shaded area is the area of a 22 by 22 square minus a circle of radius 11, so it is 4π4-\pi.

Figure BB is made of four half-size copies of figure AA, so its total shaded area is also 4π4-\pi.

In figure CC, the circle has radius 11, and the inscribed square has diagonal 22, so its area is 22. The shaded area is π2\pi-2.

Since π>3\pi>3, we have π2>4π\pi-2>4-\pi, so figure CC has the largest shaded area.

Thus, C is the correct answer.

23.

在下面的图案中,猫按顺时针方向经过四个正方形,老鼠按逆时针方向经过四个正方形外侧的八条线段。

如果图案继续下去,第 247247 次移动后猫和老鼠会在哪里?

In the pattern below, the cat moves clockwise through the four squares and the mouse moves counterclockwise through the eight exterior segments of the four squares.

If the pattern is continued, where would the cat and mouse be after the 247247th move?

答案:A
知识点:模运算找规律

难度评级:1540

解答:

猫的位置每 44 次移动重复一次,老鼠的位置每 88 次移动重复一次。

因为 2473(mod4)247\equiv3\pmod 4,猫的位置与第 33 次移动后相同:在右下方正方形。

因为 2477(mod8)247\equiv7\pmod 8,老鼠的位置与第 77 次移动后相同:在左下方正方形的左边。

所以正确答案是 A

The cat’s position repeats every 44 moves, and the mouse’s position repeats every 88 moves.

Since 2473(mod4)247\equiv3\pmod 4, the cat is in the same position as after the 33rd move: the lower right square.

Since 2477(mod8)247\equiv7\pmod 8, the mouse is in the same position as after the 77th move: the left side of the lower left square.

Thus, A is the correct answer.

24.

一艘船沿半圆路径从点 AA 到点 BB,该半圆以岛 XX 为圆心。然后它沿直线路径从 BBCC。下列哪张图最能表示船沿路线移动时到岛 XX 的距离?

A ship travels from point AA to point BB along a semicircular path, centered at Island X.X. Then it travels along a straight path from BB to C.C. Which of these graphs best shows the ship’s distance from Island XX as it moves along its course?

答案:B

难度评级:1540

解答:

AABB 的半圆路径上每一点到圆心 XX 的距离都相同,所以图像一开始是水平的。

在从 BBCC 的直线路径上,船先靠近 XX,然后远离 XX

只有图 BB 先保持水平,然后下降再上升。

所以正确答案是 B

Every point on the semicircular path from AA to BB is the same distance from the center XX, so the graph starts horizontally.

On the straight path from BB to CC, the ship first gets closer to XX and then farther away from XX.

Only graph BB starts flat and then decreases before increasing.

Thus, B is the correct answer.

25.

图中,正方形 WXYZWXYZ 的面积为 25 cm225 \text{ cm}^2。四个较小正方形边长为 11 cm,边要么与大正方形的边平行,要么重合。在 ABC\triangle ABC 中,AB=ACAB = AC,且当 ABC\triangle ABC 沿边 BC\overline{BC} 折叠时,点 AAOO(正方形 WXYZWXYZ 的中心)重合。ABC\triangle ABC 的面积是多少平方厘米?

In the figure, the area of square WXYZWXYZ is 25 cm2.25 \text{ cm}^2. The four smaller squares have sides 11 cm long, either parallel to or coinciding with the sides of the large square. In ABC,\triangle ABC, AB=AC,AB = AC, and when ABC\triangle ABC is folded over side BC,\overline{BC}, point AA coincides with O,O, the center of square WXYZ.WXYZ. What is the area of ABC,\triangle ABC, in square centimeters?

154\dfrac{15}{4}

214\dfrac{21}{4}

274\dfrac{27}{4}

212\dfrac{21}{2}

272\dfrac{27}{2}

答案:C

难度评级:1680

解答:

正方形 WXYZWXYZ 的边长为 55 cm,因为 25=5\sqrt{25} = 5

WZ\overline{WZ}BC\overline{BC} 的距离是 22,因为它等于 22 个单位正方形的边长之和。

最后,AABC\overline{BC} 的距离等于 BC\overline{BC}OO 的距离,即 2+52=92 cm 2 + \dfrac{5}{2} = \dfrac{9}{2} \text{ cm}

现在可求 BCBCWZ2=52=3 cm WZ - 2 = 5 - 2 = 3 \text{ cm}

因此 ABC\triangle ABC 的面积为 12392=274 cm2 \dfrac{1}{2} \cdot 3 \cdot \dfrac{9}{2} = \dfrac{27}{4} \text{ cm}^2

所以正确答案是 C

We get that the side lengths of WXYZWXYZ are 55 cm, since 25=5.\sqrt{25} = 5.

We also know that the distance from WZ\overline{WZ} to BC\overline{BC} is 22 since it is the sum of the side lengths of 22 unit squares.

Finally, the distance from AA to BC\overline{BC} is the same as the distance from BC\overline{BC} to O,O, which is 2+52=92 cm 2 + \dfrac{5}{2} = \dfrac{9}{2} \text{ cm}

Now, we can find BC,BC, which is WZ2=52=3 cm WZ - 2 = 5 - 2 = 3 \text{ cm}

Therefore, the area of ABC\triangle ABC is 12392=274 cm2 \dfrac{1}{2} \cdot 3 \cdot \dfrac{9}{2} = \dfrac{27}{4} \text{ cm}^2

Thus, C is the correct answer.