A boat covers 64 km in downstream in 4 hours and 48 km in upstream in 6 hours. Find the distance covered by boat in 5 hours still water?

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  1. 55
  2. 60
  3. 54
  4. 80
  5. 72

Answer (Detailed Solution Below)

Option 2 : 60
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Given:

Downstream distance = 64 km

Time taken for downstream = 4 hours

Upstream distance = 48 km

Time taken for upstream = 6 hours

Formula used:

Speed = Distance ÷ Time

Speed downstream = (Speed of boat + Speed of current)

Speed upstream = (Speed of boat - Speed of current)

Calculations:

Speed downstream = 64 ÷ 4 = 16 km/hr

Speed upstream = 48 ÷ 6 = 8 km/hr

Let the speed of the boat in still water be 'b' km/hr and the speed of the current be 'c' km/hr.

Speed downstream = b + c = 16

Speed upstream = b - c = 8

Now, solving the equations:

b + c = 16

b - c = 8

Add the two equations:

(b + c) + (b - c) = 16 + 8

2b = 24

b = 12 km/hr

The speed of the boat in still water is 12 km/hr.

Now, the distance covered by the boat in 5 hours in still water is:

Distance = Speed × Time

Distance = 12 × 5 = 60 km

∴ The distance covered by the boat in 5 hours in still water is 60 km.

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