Question

A ship is streaming towards north at a speed of $20\, kmph$ for two hours and for next $3$ hours moves towards north west with a speed $40\, km / hr$. The average speed of the ship is

• A. $30\, km / hr$
• B. $20 \sqrt{2}\, km / hr$
• C. $32\, km / hr$
• D. $20(1+\sqrt{2})\, km / hr$

Answer 1

Answer: (C)

Average speed $=\frac{\text { total distance }}{\text { total time }}$
$=\frac{\sum \text { segmentwise distances }}{\sum \text { segmentwise times }}$
average speed $=\frac{2 \times 20+3 \times 40}{5}$
$=\frac{160}{5}=32 \,km / hr$