than 去. so the mean speed cannot be simply average the 2 speeds.
Suppose the distance between A and B is X.
去Time (t1)=X/2
回time (t2)=X/1
Total time=t1+t2
Total distance=X+X
Total average speed=2X/(X/2+X/1)=4/3
Suppose the distance between A and B is X.
去Time (t1)=X/2
回time (t2)=X/1
Total time=t1+t2
Total distance=X+X
Total average speed=2X/(X/2+X/1)=4/3
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