Question

A boat goes 12 km upstream and 40 km down stream in8 hours.it can go 16 km upstream and 32 km downstream in the same time .find the speed of the boat in still water and the stream. Plz.. do it fast

Answer 1

Answer:

6Km/h   (speed of boat in still water)

2Km/h   (speed of stream)

Step-by-step explanation:

let speed of boat is x and stream is y

speed of boat upstream = x-y

speed of boat downstream = x+y

8 = 12/(x-y) + 40/(x+y)

8(x²-y²) = 52x -28y ..................(1)

8 = 16/(x-y) + 32/(x+y)

8(x²-y²) = 48x - 16y ..................(2)

(1) - (2)

4x - 12y = 0

x = 3y  .........................(3)   put in equation (1)

8(9y²-y²) = 52*3y - 28y

64y² = 128y

y = 0 or 2

y= 0 not possible 

put y = 2 in equation (3)

x = 6Km./h   (speed of boat in still water)

y = 2Km./h   (speed of stream)