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AMC12 2006 A

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AMC12 · 2006 (A)

Q1
Sandwiches at Joe's Fast Food cost $\$3$ each and sodas cost $\$2$ each. How many dollars will it cost to purchase $5$ sandwiches and $8$ sodas?
Joe快餐店的三明治每份$\$3$,汽水每份$\$2$。购买$5$份三明治和$8$份汽水一共需要多少美元?
Q2
Define $x\otimes y=x^3-y$. What is $h\otimes (h\otimes h)$?
定义$x\otimes y=x^3-y$。求$h\otimes (h\otimes h)$。
Q3
The ratio of Mary's age to Alice's age is $3:5$. Alice is $30$ years old. How old is Mary?
Mary的年龄与Alice的年龄之比为$3:5$。Alice今年$30$岁。Mary今年多少岁?
Q4
A digital watch displays hours and minutes with AM and PM. What is the largest possible sum of the digits in the display?
一块电子表以小时和分钟显示时间,并标有AM和PM。显示中各位数字之和的最大可能值是多少?
Q5
Doug and Dave shared a pizza with $8$ equally-sized slices. Doug wanted a plain pizza, but Dave wanted anchovies on half the pizza. The cost of a plain pizza was $8$ dollars, and there was an additional cost of $2$ dollars for putting anchovies on one half. Dave ate all the slices of anchovy pizza and one plain slice. Doug ate the remainder. Each paid for what he had eaten. How many more dollars did Dave pay than Doug?
Doug和Dave分享一个有$8$等分的披萨。Doug想要原味披萨,但Dave想要半个披萨加凤尾鱼。原味披萨价格为$8$美元,在一半披萨上加凤尾鱼需额外$2$美元。Dave吃了所有加凤尾鱼的披萨片以及一片原味披萨片,Doug吃了剩下的。两人各自支付自己吃掉的部分。Dave比Doug多付了多少美元?
Q6
The $8\times18$ rectangle $ABCD$ is cut into two congruent hexagons, as shown, in such a way that the two hexagons can be repositioned without overlap to form a square. What is $y$?
$8\times18$ 矩形 $ABCD$ 被切成两个全等的六边形,如图所示,使得这两个六边形可以在不重叠的情况下重新摆放成一个正方形。$y$ 是多少?
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Q7
Mary is $20\%$ older than Sally, and Sally is $40\%$ younger than Danielle. The sum of their ages is $23.2$ years. How old will Mary be on her next birthday?
Mary 比 Sally 大 $20\%$,而 Sally 比 Danielle 小 $40\%$。她们年龄之和为 $23.2$ 岁。Mary 下一个生日时多大?
Q8
How many sets of two or more consecutive positive integers have a sum of $15$?
有多少组由两个或更多连续正整数组成的数列,其和为 $15$?
Q9
Oscar buys $13$ pencils and $3$ erasers for $1.00$. A pencil costs more than an eraser, and both items cost a whole number of cents. What is the total cost, in cents, of one pencil and one eraser?
Oscar 用 $1.00$ 美元买了 $13$ 支铅笔和 $3$ 个橡皮。铅笔比橡皮贵,并且两种物品的价格都是整数美分。一支铅笔和一个橡皮的总价(美分)是多少?
Q10
For how many real values of $x$ is $\sqrt{120-\sqrt{x}}$ an integer?
有多少个实数 $x$ 使得 $\sqrt{120-\sqrt{x}}$ 是整数?
Q11
Which of the following describes the graph of the equation $(x+y)^2=x^2+y^2$?
以下哪个描述了方程 $(x+y)^2=x^2+y^2$ 的图像?
Q12
A number of linked rings, each $1$ cm thick, are hanging on a peg. The top ring has an outside diameter of $20$ cm. The outside diameter of each of the outer rings is $1$ cm less than that of the ring above it. The bottom ring has an outside diameter of $3$ cm. What is the distance, in cm, from the top of the top ring to the bottom of the bottom ring?
有若干个相连的环,每个环厚 $1$ cm,挂在一个挂钩上。最上面的环外径为 $20$ cm。其余每个外侧环的外径都比它上面的环小 $1$ cm。最下面的环外径为 $3$ cm。从最上面环的顶部到最下面环的底部的距离是多少(单位:cm)?
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Q13
The vertices of a $3-4-5$ right triangle are the centers of three mutually externally tangent circles, as shown. What is the sum of the areas of the three circles?
一个 $3-4-5$ 直角三角形的顶点是三个两两外切的圆的圆心,如图所示。三个圆的面积之和是多少?
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Q14
Two farmers agree that pigs are worth $300$ dollars and that goats are worth $210$ dollars. When one farmer owes the other money, he pays the debt in pigs or goats, with "change" received in the form of goats or pigs as necessary. (For example, a $390$ dollar debt could be paid with two pigs, with one goat received in change.) What is the amount of the smallest positive debt that can be resolved in this way?
两位农民约定猪值 $300$ 美元,山羊值 $210$ 美元。当一位农民欠另一位钱时,他用猪或山羊来偿还债务,并在需要时以山羊或猪的形式收取“找零”。(例如,$390$ 美元的债务可以用两头猪支付,并收到一只山羊作为找零。)能够用这种方式结清的最小正债务金额是多少?
Q15
Suppose $\cos x=0$ and $\cos (x+z)=1/2$. What is the smallest possible positive value of $z$?
设 $\cos x=0$ 且 $\cos (x+z)=1/2$。$z$ 的最小可能正值是多少?
Q16
Circles with centers $A$ and $B$ have radius 3 and 8, respectively. A common internal tangent intersects the circles at $C$ and $D$, respectively. Lines $AB$ and $CD$ intersect at $E$, and $AE=5$. What is $CD$?
中心分别为 $A$ 和 $B$ 的圆分别有半径 3 和 8。一个公共内切线分别与圆相交于 $C$ 和 $D$。直线 $AB$ 和 $CD$ 相交于 $E$,且 $AE=5$。求 $CD$ 的长。
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Q17
Square $ABCD$ has side length $s$, a circle centered at $E$ has radius $r$, and $r$ and $s$ are both rational. The circle passes through $D$, and $D$ lies on $\overline{BE}$. Point $F$ lies on the circle, on the same side of $\overline{BE}$ as $A$. Segment $AF$ is tangent to the circle, and $AF=\sqrt{9+5\sqrt{2}}$. What is $r/s$?
正方形 $ABCD$ 边长为 $s$,以 $E$ 为中心的圆半径为 $r$,且 $r$ 和 $s$ 均为有理数。该圆经过 $D$,且 $D$ 位于 $\overline{BE}$ 上。点 $F$ 位于圆上,位于 $\overline{BE}$ 与 $A$ 同侧。线段 $AF$ 切于圆,且 $AF=\sqrt{9+5\sqrt{2}}$。求 $r/s$?
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Q18
The function $f$ has the property that for each real number $x$ in its domain, $1/x$ is also in its domain and $f(x)+f\left(\frac{1}{x}\right)=x$ What is the largest set of real numbers that can be in the domain of $f$?
函数 $f$ 具有如下性质:对其定义域中的每个实数 $x$,$1/x$ 也在其定义域中,且 $f(x)+f\left(\frac{1}{x}\right)=x$ $f$ 的定义域中可能包含的最大实数集合是什么?
Q19
Circles with centers $(2,4)$ and $(14,9)$ have radii $4$ and $9$, respectively. The equation of a common external tangent to the circles can be written in the form $y=mx+b$ with $m>0$. What is $b$?
中心分别为 $(2,4)$ 和 $(14,9)$ 的圆分别有半径 $4$ 和 $9$。两个圆的一个公共外切线的方程可写成 $y=mx+b$ 的形式,其中 $m>0$。求 $b$。
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Q20
A bug starts at one vertex of a cube and moves along the edges of the cube according to the following rule. At each vertex the bug will choose to travel along one of the three edges emanating from that vertex. Each edge has equal probability of being chosen, and all choices are independent. What is the probability that after seven moves the bug will have visited every vertex exactly once?
一只虫子从一个立方体的一个顶点出发,按照如下规则沿立方体棱移动。在每个顶点,虫子将选择从该顶点发出的三条棱之一进行移动。每条棱被选择的概率相等,且所有选择相互独立。七步移动后虫子恰好访问每个顶点一次的概率是多少?
Q21
Let $S_1=\{(x,y)|\log_{10}(1+x^2+y^2)\le 1+\log_{10}(x+y)\}$ and $S_2=\{(x,y)|\log_{10}(2+x^2+y^2)\le 2+\log_{10}(x+y)\}$. What is the ratio of the area of $S_2$ to the area of $S_1$?
设 $S_1=\{(x,y)|\log_{10}(1+x^2+y^2)\le 1+\log_{10}(x+y)\}$ 和 $S_2=\{(x,y)|\log_{10}(2+x^2+y^2)\le 2+\log_{10}(x+y)\}$。 $S_2$ 的面积与 $S_1$ 的面积之比是多少?
Q22
A circle of radius $r$ is concentric with and outside a regular hexagon of side length $2$. The probability that three entire sides of hexagon are visible from a randomly chosen point on the circle is $1/2$. What is $r$?
半径为 $r$ 的圆与边长为 $2$ 的正六边形同心且位于其外部。从圆上随机选取一点,能看到正六边形的三条完整边的概率为 $1/2$。求 $r$。
Q23
Given a finite sequence $S=(a_1,a_2,\ldots ,a_n)$ of $n$ real numbers, let $A(S)$ be the sequence $\left(\frac{a_1+a_2}{2},\frac{a_2+a_3}{2},\ldots ,\frac{a_{n-1}+a_n}{2}\right)$ of $n-1$ real numbers. Define $A^1(S)=A(S)$ and, for each integer $m$, $2\le m\le n-1$, define $A^m(S)=A(A^{m-1}(S))$. Suppose $x>0$, and let $S=(1,x,x^2,\ldots ,x^{100})$. If $A^{100}(S)=(1/2^{50})$, then what is $x$?
给定由 $n$ 个实数组成的有限序列 $S=(a_1,a_2,\ldots ,a_n)$,令 $A(S)$ 为由 $n-1$ 个实数组成的序列 $\left(\frac{a_1+a_2}{2},\frac{a_2+a_3}{2},\ldots ,\frac{a_{n-1}+a_n}{2}\right)$。 定义 $A^1(S)=A(S)$,并对每个整数 $m$($2\le m\le n-1$)定义 $A^m(S)=A(A^{m-1}(S))$。设 $x>0$,令 $S=(1,x,x^2,\ldots ,x^{100})$。若 $A^{100}(S)=(1/2^{50})$,求 $x$。
Q24
The expression \[(x+y+z)^{2006}+(x-y-z)^{2006}\] is simplified by expanding it and combining like terms. How many terms are in the simplified expression?
将表达式 \[(x+y+z)^{2006}+(x-y-z)^{2006}\] 展开并合并同类项后得到简化式。简化后的表达式共有多少项?
Q25
How many non- empty subsets $S$ of $\{1,2,3,\ldots ,15\}$ have the following two properties? $(1)$ No two consecutive integers belong to $S$. $(2)$ If $S$ contains $k$ elements, then $S$ contains no number less than $k$.
集合 $\{1,2,3,\ldots ,15\}$ 的非空子集 $S$ 有多少个满足以下两个条件? $(1)$ $S$ 中不包含两个相邻的整数。 $(2)$ 若 $S$ 含有 $k$ 个元素,则 $S$ 中不包含任何小于 $k$ 的数。
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