Question

A motorboat covers a distance of

16km upstream and 24km downstream

in 6 hours. In the same time it covers a

distance of 12 km upstream and 36km

downstream. Find the speed of the boat

in still water and that of the stream.

5​

Answer 1

Answer:

ANSWER

Let speed of the boat in still water =x km/hr, and

Speed of the current =y km/hr

Downstream speed =(x+y) km/hr

Upstream speed =(x−y) km/hr

T=  S /D

​x+y /24  +  x−y /16=6          .......(1)

x+y/36  +  x−y /12 =6          .......(2)

Put  

x+y  =1/u and  

x−y  =1/v the above equation becomes,

24u+16v=6

Or, 12u+8v=3               ... (3)

36u+12v=6

Or, 6u+2v=1                ... (4)

Multiplying (4) by 4, we get,

24u+8v=4v                  … (5)

Subtracting (3) by (5), we get,

12u=1

⇒u=  1 /12

Putting the value of u in (4), we get, v=  1 /4

⇒x+y=12 and x−y=4

2x = 16 =>x = 8

and 8 + y = 12 => y = 4

Thus, speed of the boat in still water =8 km/hr

Speed of the boat in stream = 4 km/hr

Answer 2

speed of motorboat downstream = 8 km/hr

speed of motorboat upstream = 4km/hr

see the pic that i had attached

hope this helps...