Answer
68kmh
Work Step by Step
One can find the average speed in this equation by dividing the total distance by the elapsed time. For simplicity's sake, the total distance will be set equal to 100km (Although it would work for any distance). Each speed will travel half the distance: 50 miles.---Speed=miles$\div$hours
90km/h=50miles$\div$hours
.556 hours
55km/h=50miles$\div$hours
.909hours
Total time= .909 +.556
Total time= 1.465 hours
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100miles$\div$ 1.465 hours=Average speed
Average speed= 68.276kmh
