Question

下列哪个式子等于

$\frac{9}{7 \times 53}$

Which of the following is equal to

$\frac{9}{7 \times 53}?$

$\dfrac{.9}{.7 \times 53}$

$\dfrac{.9}{.7 \times .53}$

$\dfrac{.9}{.7 \times 5.3}$

$\dfrac{.9}{7 \times .53}$

$\dfrac{.09}{.07 \times .53}$

答案：A

知识点：分数位值

难度评级：920

解答：

将分子 $9$ 除以 $10$ ，得到 $.9$ 。为了保持分数值不变，分母整体也要除以 $10$ ，即把其中一个因数除以 $10$ 。

把分母中的因数 $7$ 除以 $10$ ，而另一个因数保持不变，便得到 $\frac{.9}{.7 \times 53}$ 。其他选项会使原式改变 $10$ 倍或 $100$ 倍。

所以正确答案是 A。

To rewrite the numerator $9$ as $.9,$ divide it by $10.$ To keep the fraction equal, divide the denominator by $10$ too, which means dividing one of its factors by $10.$

Dividing the factor $7$ by $10$ gives $\frac{.9}{.7 \times 53},$ which equals the original. Each other choice changes the value by a factor of $10$ or $100.$

Thus, the correct answer is A .

1989 AMC 8 第 13 题

答案：A

难度评级：920

解答：

其他年份的第 13 题