单选题
If a is increased by 25% and b is decreased by 25%, the resulting numbers will be equal. What is the ratio of a to b?
【正确答案】
A
【答案解析】a+25%(a)= 1.25a, andb-25%(b)=0.75b. So, 1.25a = .75b, and [*]
**If after increasing a and decreasing b the results are equal, a must be smaller than b. So, the ratio of a to b must be less than 1.
Eliminate Choices C, D, and E. Now, either test Choices A and B or just guess. To test Choice B, pick two numbers in the ratio of 3 to 4 30 and 40, for example. Then, 30 increased by 25% is 37.5, and 40 decreased by 25% is 30. The results are not equal, so eliminate Choice B. The answer is [*]. (50 decreased by 25% is 37.5.)
**If after increasing a and decreasing b the results are equal, a must be smaller than b. So, the ratio of a to b must be less than 1.
Eliminate Choices C, D, and E. Now, either test Choices A and B or just guess. To test Choice B, pick two numbers in the ratio of 3 to 4 30 and 40, for example. Then, 30 increased by 25% is 37.5, and 40 decreased by 25% is 30. The results are not equal, so eliminate Choice B. The answer is [*]. (50 decreased by 25% is 37.5.)