Question

A man rows 750 m in 600 seconds against the stream and returns in $7\frac{1}{2}$ minutes. Its rowing speed in still water is (in km/ hr).

• A. 5.5
• B. 5.75
• C. 5
• D. 5.25

Answer 1

Answer:

D. 5.25

Rate downstream $=\frac{(\frac{750}{15})}{2} m/minute$

$=100 m/minute$

$=\frac{100\times{60}}{1000}kmph=6kmph$

Rate upstream $=(\frac{750}{600}\times{\frac{18}{5}})kmph$

$=4.5kmph$

Rowing speed in still water $=\frac{1}{2}(6+4.5)=\frac{10.5}{2}$

$=5.25kmph$