问题
单项选择题
A certain ear increased its average speed by 5 miles per hour in each successive 5-minute interval after the first interval. If in the first 5-minute interval its average speed was 20 miles per hour, how many miles did the car travel in the third 5-minute interval ？（）
A．1.0
B．1.5
C．2.0
D．2.5
E．3.0
答案
参考答案：D
解析：
根据题意可得第三个5分钟内小汽车的平均速度为：
20+5+5=30英里/小时
所以第三个5分钟行驶的里程为2.5。