请教1个难题？

linlin2008

Laura borrowed $2400 from her parents to pay for her college education. If she pays back 2½ percent of this amount quarterly, and she has paid back $420, for how many months has she been paying back for her loan?

A. 6; B 7; C. 21: D. 24; E. 28.

The answer is C.

请问NN， 这题该怎么计算。 非常感谢

mikejia

每个季度3个月。 7*3=21。7你自己应该已经算出来了：）

himba

这里主要是quarterly的理解，quarterly=一年四次的，每季度的；

2400*0.025=60；

420/60=7；所以出现了7次季度性支付；

一个季度有3个月，7*3=21