Question

一个盒子里装有三角形瓷砖和正方形瓷砖，共 $25$ 块。这些瓷砖一共有 $84$ 条边。盒子里有多少块正方形瓷砖？

A box contains a collection of triangular and square tiles. There are $25$ tiles in the box, containing $84$ edges total. How many square tiles are there in the box?

$3$

$5$

$7$

$9$

$11$

答案：D

知识点：方程组

难度评级：870

解答：

设三角形瓷砖有 $x$ 块，正方形瓷砖有 $y$ 块，则且把第一个方程乘以 $3$ ，得到，两式相减得 $y = 9$ 。 $x + y = 25$ $3x + 4y = 84.$ $3x + 3y = 75$

所以正确答案是 D。

Let $x$ be the number of triangular tiles and $y$ be the number of square tiles. We then have that $x + y = 25$ and $3x + 4y = 84.$ Multiplying the first equation by $3$ gives us $3x + 3y = 75$ and subtracting this from the other equation gives us $y = 9.$

Thus, D is the correct answer.

2015 AMC 10A 第 2 题

答案：D

难度评级：870

解答：

其他年份的第 2 题