Question

Tori 的数学测试有 $75$ 道题： $10$ 道算术题、 $30$ 道代数题和 $35$ 道几何题。她答对了 $70\%$ 的算术题、 $40\%$ 的代数题和 $60\%$ 的几何题，但因为答对题数少于 $60\%$ ，所以没有通过测试。

她还需要多答对多少道题，才能达到 $60\%$ 的及格分数？

Tori's mathematics test had $75$ problems: $10$ arithmetic, $30$ algebra, and $35$ geometry problems. Although she answered $70\%$ of the arithmetic, $40\%$ of the algebra, and $60\%$ of the geometry problems correctly, she did not pass the test because she got less than $60\%$ of the problems right.

How many more problems would she have needed to answer correctly to earn a $60\%$ passing grade?

$1$

$5$

$7$

$9$

$11$

答案：B

知识点：百分数

难度评级：1230

解答：

她答对了 $10 \cdot .7 = 7$ 道算术题，答对了 $30 \cdot .4 = 12$ 道代数题，还答对了 $35 \cdot .6 = 21$ 道几何题。

因此她总共答对 $7 + 12 + 21 = 40$ 道题。

要达到 $60\%$ ，Tori 必须答对道题。所以她还需要多答对 $45 - 40 = 5$ 道题。 $75 \cdot .6 = 45$

所以正确答案是 B。

She answered $10 \cdot .7 = 7$ arithmetic questions correctly. She answered $30 \cdot .4 = 12$ algebra ones correctly. She also got $35 \cdot .6 = 21$ geometry questions correctly.

This means she got a total of $7 + 12 + 21 = 40$ questions correct.

As such, in order to get a $60\%,$ Tori must have answered $75 \cdot .6 = 45$ questions correctly. This means that she would have needed to answer an additional $45 - 40 = 5$ questions correctly.

Thus, B is the correct answer.

1999 AMC 8 第 16 题

答案：B

难度评级：1230

解答：

其他年份的第 16 题