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A boat covered 24 km upstream and 20 km downstream. If the speed of the boat in still water is 6 km/hr and speed of stream is 4 km/hr then, find the total time taken to cover whole journey.
1. 16 hours
2. 14 hours
3. 12 hours
4. 10 hours

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Correct Answer - Option 2 : 14 hours

Given:

Distance covered upstream = 24 km

Distance covered downstream = 20 km

Speed of boat in still water = 6 km/hr

Speed of stream = 4 km/hr

Concept used:

Upstream speed = Speed of boat in still water – Speed of stream

Downstream speed = Speed of boat in still water + Speed of stream

Calculation:

Upstream speed = (6 – 4) km/hr

⇒ 2 km/hr

Downstream speed = (6 + 4) km/hr

⇒ 10 km/hr

Time taken to cover 24 km upstream = 24/2 hours

⇒ 12 hours

Time taken to cover 20 km downstream = 20/10 hours

⇒ 2 hours

Total time taken to cover the whole journey = (12 + 2) hours

⇒ 14 hours

∴ The total time taken to cover whole journey is 14 hours

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