Question

To go a certain distance of 40 km upstream a rower takes 8 hours while it takes her only 5 hours to row the same distance downstream. What was the rower’s speed in still water?

• A. 1.5 km/h
• B. 4.5 km/h
• C. 6.5 km/h
• D. 4 km/h

Answer 1

Answer:

C. 6.5 km/h

Let x be the rower’s speed and y be the current speed of water.

Speed while going upstream = (x –y)

$⇒\frac{40}{(x-y)}=8$

⇒ x – y = 5      ---- (1)

Now speed while going downstream = (x + y)

$⇒\frac{40}{(x+y)}=5$

⇒ x + y = 8      ----(2)

From equation 1 and 2 we get

x = 6.5 km/hr

∴ Rower’s speed = 6.5 km/hr