Question

哪一对数的乘积不等于 $36$ ？

Which pair of numbers does not have a product equal to $36?$

$\{-4, -9\}$

$\{-3, -12\}$

$\left\{\dfrac12, -72\right\}$

$\{1, 36\}$

$\left\{\dfrac32, 24\right\}$

知识点：分数

把每一对中的两个数相乘，检查哪个乘积不是 $36$

Multiply the two numbers in each pair and check which product is not $36$

负数乘负数是正数；特别注意 $\dfrac12 \times (-72)$ 的符号

A negative times a negative is positive, so watch the signs of $\dfrac12 \times (-72)$

逐项检查： $(-4)(-9) = 36$ ， $(-3)(-12) = 36$ ， $\dfrac12 \times (-72) = -36$ ， $(1)(36) = 36$ ，且 $\dfrac32 \times 24 = 36$ 。

只有 $\dfrac12 \times (-72) = -36$ 不等于 $36$ 。

所以正确答案是 C。

Checking each pair: $(-4)(-9) = 36,$ $(-3)(-12) = 36,$ $\dfrac12 \times (-72) = -36,$ $(1)(36) = 36,$ and $\dfrac32 \times 24 = 36.$

Only $\dfrac12 \times (-72) = -36$ fails to equal $36.$

Thus, the correct answer is C .