1998 AMC 8 第 7 题

Question

100\times 19.98\times 1.998\times 1000=

(1.998)^2

(19.98)^2

(199.8)^2

(1998)^2

(19980)^2

知识点：小数指数

把小数因数与

10

的幂配对

Pair the factors with powers of

10.

将乘积写成

(100\cdot 19.98)(1000\cdot 1.998)

。

Group the product as

(100\cdot 19.98)(1000\cdot 1.998).

把前两个因数和后两个因数分别分组：

\begin{aligned} &(100\cdot 19.98)(1.998\cdot 1000) \\ &= 1998\cdot1998 \\ &= (1998)^2 \end{aligned}\text{。}

所以正确答案是 D。

Group the first two factors and the last two factors:

\begin{aligned} &(100\cdot 19.98)(1.998\cdot 1000) \\ &= 1998\cdot1998 \\ &= (1998)^2. \end{aligned}

Thus, the correct answer is D .

其他年份的第 7 题