A man can row a boat at 8 km/h in still water. If the speed of the water current is 2 km/h and it takes him 2 hours to row to a place and come back, then how far off (in km) is the place?

7.5

The correct answer is Option (1) → 7.5

Speed of the boat = 8km/h

Speed of the current = 2km/h

Downstream speed = Speed of the boat + Speed of the current = 8 + 2 = 10 km/h

Time = \(\frac{Distance}{Speed}\)

Upstream speed = Speed of the boat - Speed of the current = 8 - 2 = 6km/h

According to the question,

 \(\frac{D}{10}\) +  \(\frac{D}{6}\) = 2

 \(\frac{3D + 5D}{30}\) = 2

8D = 60

D = 7.5 km