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考题1-3 2015 AMC 10B

2018-08-06 重点归纳

AMC10数学竞赛是美国高中数学竞赛中的一项，是针对高中一年级及初中三年级学生的数学测试，该竞赛开始于2000年，分A赛和B赛，于每年的2月初和2月中举行，学生可任选参加一项即可。不管是对高校申请还是今后在数学领域的发展都极其有利！那么接下来跟随小编来看一下AMC10的官方真题以及官方解答吧：

Problem1

What is the value of $2-(-2)^{-2}$ ?

$考题1-3 2015 AMC 10B$

Solution

$考题1-3 2015 AMC 10B$

Problem2

Marie does three equally time-consuming tasks in a row without taking breaks. She begins the first task at 1:00 PM and finishes the second task at 2:40 PM. When does she finish the third task?

$\textbf{(A) }\text{3:10 PM}\qquad\textbf{(B) }\text{3:30 PM}\qquad\textbf{(C) }\text{4:00 PM}\qquad\textbf{(D) }\text{4:10 PM}\qquad\textbf{(E) }\text{4:30 PM}$

Solution

Marie does her work twice in $1$ hour and $40$ minutes. Therefore, one task should take $50$ minutes to finish. $50$ minutes after $2\!:\!40$ PM is $3\!:\!30$ PM, so our answer is $\boxed{\textbf{(B) }\text{3:30 PM}}$

Problem3

Isaac has written down one integer two times and another integer three times. The sum of the five numbers is $100$ , and one of the numbers is $28$ . What is the other number?

$考题1-3 2015 AMC 10B$

Solution

Let the first number be $x$ and the second be $y$ . We have $2x+3y=100$ . We are given one of the numbers is $28$ . If $x$ were to be $28$ , $y$ would not be an integer, thus $y=28$ . $2x+3(28)=100$ , which gives $x=\boxed{\textbf{(A) }8}$ .