[请教]XDF数学 66

A family made a down payment of $75 and borrowed the balance on a set of encyclopedias that cost $400. The balance with interest was paid in 23 monthly payment of $16 each and a final payment of $9. The amount of interest paid was what percent of the amount borrowed?

a. 6%

b. 12%

c. 14%

d. 16%

e. 20%

我的解题过程：

总共付了$75+23*$16+9=$452

interest=$452-$400=$52

so 52/400=13%

哪儿不对了？谢谢~~~

哦！！！我明白了。

去掉down payment,其实借了400-75=$325

interest=23*16+9-325=52

so 52/325=16%

不好意思~~~麻烦大家了