[求助]PP PS2

88. 9789-!-item-!-187;#058&007104
In May Mrs. Lee's earnings were 60 percent of the Lee family's total income.  In June Mrs. Lee earned 20 percent more than in May.  If the rest of the family's income was the same both months, then, in June, Mrs. Lee's earnings were approximately what percent of the Lee family's total income?

(A) 64%
(B) 68%
(C) 72%
(D) 76%
(E) 80%

答案是A

不過我算C~"~

看了好久  請大大解答  謝謝

你应该是在计算时，6月的总收入少算了。讲一个简单好理解的。假设李太太5月收入60元，那么这个月的家庭收入为100元（60/60%=100）6月，李太太收入60*（1+20%）=72元，比上个月多12元，同时家庭总收入也变为100+12=112元，李太太收入占家庭总收入的比例为72/112=64%。如果用方程，则设李太太5月的收入为X，则5月的家庭收入为X/60%，6月李太太的收入为X（1+20%），家庭收入为X/60%+20%X。也得64%