# A man runs at 30 km/h for first 45 km and for next 30 km, he runs at a speed of 10 km/h. Find the average speed.

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A man runs at 30 km/h for first 45 km and for next 30 km, he runs at a speed of 10 km/h. Find the average speed.

1. 70/9 km/h
2. 50/3 km/h
3. 2/7 km/h
4. 5/7 km/h

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Correct Answer - Option 2 : 50/3 km/h

Given

Speed for 45 km = 30 km/h

Speed for 30 km = 10 km/h

Formula used

Average speed = Total distance travelled/Total time taken

Time = Distance/Speed

Calculation

Time taken to travel 45 km at a speed of 30 km/h= 45/30

⇒ 1.5 hours

Time taken to travel 30 km at a speed of 10 km/h = 30/10

⇒ 3 hours

Total time taken = 1.5 + 3

⇒ 4.5 hours

Total distance travelled = 45 + 30

⇒ 75 km

Average speed = 75/4.5

⇒ 50/3 km/h

∴ Average speed is (50/3) km/h