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题库 / OG2017Q-PS-26
Of the total amount that Jill spent on a shopping trip, excluding taxes, she spent 50 percent on clothing, 20 percent on food, and 30 percent on other items. If Jill paid a 4 percent tax on the clothing, no tax on the food, and an 8 percent tax on all other items, then the total tax that she paid was what percent of the total amount that she spent, excluding taxes?
2.8%
3.6%
4.4%
5.2%
6.0%
题目分析：
首先假设 Jill 一共的花费是 X 元；clothing 不含 tax 就是 50%*X, food 不 tax 就是 20%*X，其他东西就是 30%*X,买衣服的 tax 就是 50%*X*4%,food tax=0,other items
tax=30%*X*8%;所求的比例=(50%*X*4%+30%*X*8%)/X,约分去掉 X,化简得，4.4%。
综上：答案就是 4.4%.
50%X是不含税的amount，为什么可以直接乘以4%？不应该是50%X/0.96*0.04才是实际付的税吗？
Therefore, the total amount of tax Jill paid was (0.04)(0.5T) + (0.08)(0.3T) = 0.02T + 0.024T = 0.044T. The tax as a percent of the total amount Jill spent, excluding taxes, was4.4%
Let T represent the total amount Jill spent, excluding taxes. Jill paid a 4% tax on the clothing she bought, which accounted for 50% of the total amount she spent, and so the tax she paid on the clothing was (0.04)(0.5T). Jill paid an 8% tax on the other items she bought, which accounted for 30% of the total amount she spent, and so the tax she paid on the other items was (0.08)(0.3T).
（4*0.5+3*0.8）%=4.4%
老师，这里不是求tax在除去tax后的商品价格里所占比重么，为何不是4.4%/95.6%？
算出来的4.4%已经是tax在除税消费的比重了。
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