A certain bridge is 4,024 feet long. Approximately how many minutes does it take to cross this bridge at a constant speed of 20 miles per hour? (1 mile = 5,280 feet)

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##### 考题讲解

~$4024 feet=\frac{4024}{5280} mile$~所求的时间~$t=\frac{4024}{5280}/20=\frac{4024}{5280*20} h$~