Respuesta :
[tex] \boxed {\text {Time = Distance} \div \text{Speed}} [/tex]
Given Distance = 68km Speed = 51 km/h:
Time = 68 ÷ 51 = 1 1/3 hour
Given Distance = 20km, Speed = 40 km/h:
Time = 20 ÷ 40 = 1/2 hour
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Find Total Distance:
Total Distance = 68 + 20 = 88km
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Find Total Time Taken:
Total Time = 1 1/3 + 1/2 = 1 5/6 hours
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Find Average Speed:
Speed = 88 ÷ 1 5/6 = 48 km/hour
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Answer: Average speed = 48 km/hour
time = distance / rate
travelling 68 km at 51 km/hour = 1 + (1/3) hours
travelling 20 km at 40 km/hour = .50 hours
total time = 1.8333333... hours
total distance = 68 + 20 = 88 kilometers
average speed = 88 km / 1.8333333... hours
average speed = 48 km / hour