AMC 8 2009 Problem 8
AMC8 2009 年第 8 题
百分比★★☆☆☆
The length of a rectangle is increased by 10% percent and the width is decreased by 10% percent. What percent of the old area is the new area?
矩形的长增加了 10％，宽减小了 10％，那么新的矩形面积是原来的面积的百分之多少？
- A.90
- B.99
- C.100
- D.101
- E.110
正确答案 · Correct Answer
B
解析 · Solution
Solution 1
In a rectangle with dimensions 10×10, the new rectangle would have dimensions 11×9. The ratio of the new area to the old area is .
If you take the length as and the width as then A(OLD)= $xy$. 0.99=99%
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