2019年AMC12真题PDF下载-A卷
1. The area of a pizza with radius 4 is N percent larger than the area of a pizza with radius 3 inches. What is the integer closest to N ?
半径为4 英寸的比萨饼面积比半径为3 英寸的比萨饼面积大的百分数是N。问最接近N 的整数是什么?
(A)25 (B)33 (C)44 (D)66 (E)78
2.Suppose a is 150% of b . What percent of a is 3b ?
假设a 是b 的150%。 那么a 的百分之多少是3b?
(A)50 (B)66 (C)150 (D)200 (E)450
3. A box contains 28 red balls, 20 green balls, 19 yellow balls, 13 blue balls, 11 white balls, and 9 black balls. What is the minimum number of balls that must be drawn from the box without replacement to guarantee that at least 15 balls of a single color will be drawn?
一个盒子中有28 个红球，20个绿球，19个黄球，13个蓝球，11个白球和9个黑球。为了保证至少取出15 个单一颜色的球,在不允许放回重取的情况下，必须从盒子里取出的球的数量最少是多少个?
(A)75 (B)76 (C)79 (D)84 (E)91
4. What is the greatest number of consecutive integers whose sum is 45?
最多可以有多少个连续整数，它们的总和是45?
(A)9 (B)25 (C)45 (D)90 (E)120
5. Two lines with slopes 1/2 and 2 intersect at (2,2) . What is the area of the triangle enclosed by these two lines and the line x + y =10 ?
两条斜率分别为1/2和2的直线相交于(2, 2)。问由这两条直线和直线x + y = 10所框出的三角形的面积是多少?
(A)4 (B)4√2 (C)6 (D)8 (E)6√2
6. The figure below shows line λ with a regular, infinite, recurring pattern of squares and line segments.
下图显示了直线l ，该直线由规则的、无限的、重复出现的正方形和线段所组成的图形。
How many of the following four kinds of rigid motion transformations of the plane in which this figure is drawn, other than the identity transformation, will transform this figure into itself?
在下面的四种关于该图形所在平面的刚性变换中，有几种是除了恒等变换外，能够把上述图形变到自身的?
some rotation around a point of line λ
围绕直线A 上的某个点的旋转
some translation in the direction parallel to line λ
沿着平行于直线A 的方向的某个平移
the reflection across line λ
关于直线A 的反射
some reflection across a line perpendicular to line λ
关于某条垂直于直线A 的直线的反射
(A)0 (B)1 (C)2 (D)3 (E)4
7. Melanie computes the mean μ , the median M , and the modes of the 365 values that are the dates in the months of 2019. Thus her data consist of 12 1s , 12 2s , . . . ,12 28s , 11 29s , 11 30s , and 7 31s . Let d be the median of the modes. Which of the following statements is true?
Melanie 计算2019 年的各个月的日期这365个数值的平均数μ，中位数M以及众数。因此，她的数据包括12个1，12个2，··· ，12个28，11个29，11个30以及7个31。设d为众数的中位数。下列哪个论断是正确的?
(A)μ<d<M (B)M<d<μ (C)d=M=μ (D)d<M<μ (E)d<μ<M
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