A man rows 8 km h in still water If the river is running at 2 km h it takes 32 min to row to a place...........

Quant (SSC) Boats and Streams

A man rows 8 km/h in still water. If the river is running at 2 km/h, it takes 32 min to row to a place and back. How far is the place?

1.5 km

2.5 km

2 km

3 km

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Explanation:

A person can row a a speed of ‘x’ in still water. If stream is flowing at a speed of ‘y’,
it takes time ‘T’ to row to a place and back, then distance
between two placed is given by T(x² – y²) /2x
Given,
Total Time (T) = 32 min = 32/60 = 8/15 hr
By the short trick approach, we get
= [8/15 × {(8)² – (2)²/ 2 x 8]km
= 8 × {64 – 4} /15 × 2 × 8
= 8 x 60 /15 x 16 = 2 km