Question

Ritu can row downstream 20 km in 2 hour and upstream in 4 km in 2 hour find highest speed over rowing in still water and speed of current

Answer 1

u = speed of boat
v = speed of water current

speed of boat in upstream = u - v
speed of boat in downstream = u + v

speed of boat in upstream :--
= distance ÷ time
= 4÷2
= 2

speed of boat in downstream :---
=distance ÷ time
= 20 ÷ 2
= 10
so,
u + v = 10. -- 1
u - v = 2. -- 2

solving the equations by substitution method,

u = 10 - v

substitute this value to 2 gives,

10 - v - v = 2
10-2v=2
-2v = -8
v = -8÷-4
= 4

substitute this value of v to 1 to get,

u = 10 - 4
= 6

So, the speed of boat in still water is 6 Km/hr
and the speed of water current is 4 km / hr
----------------------------------------------------------------------
Hope it helps.