A man travels from P to Q at the speed of 60 km/h and travels from Q to P at the speed of 90 km /h. What is the average speed of the man fo rhe whole journey?
Show answer & explanation
Correct answer: D
Explanation
The Correct Answer is option 4 i.e. 72 km/h
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Understanding |
Application |
Calculation |
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Speed (P to Q) = 60 km/hr Speed (Q to P) = 90 km/hr |
Suppose the distance PQ = 180 km (LCM of 60 & 90) So, Total distance = 360 km |
⇒ 180 + 180 = 360 |
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We need to calculate total time of whole journey |
So, Total time = 5 hours |
⇒ 180/60 + 180/90 = 3 + 2 = 5 |
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Speed = Distance/Time |
Hence, Avg speed of whole journey = 72 km/hr |
⇒ 360/5 = 72 |