15. The rear wheels of a car crossed a
certain line 0.5 second after the front
wheels crossed the same line. If the
centers of the front and rear wheels
are 20 feet apart and the car traveled
in a straight line at a constant speed,
which of the following gives the speed
of the car in miles per hour? (5,280
feet = 1 mile)
 此主题相关图片如下：
| 
