AMC8 1991

AMC8 1991 · Q7

AMC8 1991 · Q7. It mainly tests Rounding & estimation.

The value of $\frac{(487,000)(12,027,300) + (9,621,001)(487,000)}{(19,367)(.05)}$ is closest to

$ \frac{(487,000)(12,027,300) + (9,621,001)(487,000)}{(19,367)(.05)}$ $的值最接近

(A) 10,000,000 10,000,000

(B) 100,000,000 100,000,000

(D) 10,000,000,000 10,000,000,000

(E) 100,000,000,000 100,000,000,000

Answer

Correct choice: (D)

正确答案：（D）

Solution

Rounding each number to one significant digit (highest place value) yields $(500,000)(10,000,000) + (10,000,000)(500,000) / (20,000)(.05)$ which equals $(500,000)(10,000,000 + 10,000,000) / 1,000$ which equals $(500)(20,000,000) = 10,000,000,000$.

将每个数字四舍五入到一位有效数字（最高位值）得到 $(500,000)(10,000,000) + (10,000,000)(500,000) / (20,000)(.05)$，等于 $(500,000)(10,000,000 + 10,000,000) / 1,000$，等于 $(500)(20,000,000) = 10,000,000,000$。

Topics

AR.011 Rounding & estimation