speed of a boat in still water is 15km/hr. if the time taken to travel 30 km downstream and then the same distance upstream is 4 hours 10 min. find the speed of flow of water
Answers
Answered by
2
Speed of flow of water is 3 kmph.
Answered by
9
Speed of boat = 15 km/hr
Let speed of water = y km/hr
Upstream speed = 15 - y
Downstream speed= 15 + y
Given: Downstream dist/down speed + Up dist/Up speed = 4 hours 10 mins.
[D/S = T, formula used]
30/15+y + 30/15-y = 4 10/60 = 4 1/6 hrs = 25/6 hours
30[(1/15+y) + (1/15-y)] = 25/6
(15 - y + 15 + y)/(15-y)*(15+y) = 25/6*30
30/225-y^2 = 25/180
180*30 = 25*(225-y^2)
[Divide L.H.S & R.H.S by 25]
216 = 225 - y^2
y^2 = 9
y = 3 km/hr
Hence, speed of flow of water = 3 km/hr.
Hope it helps
Let speed of water = y km/hr
Upstream speed = 15 - y
Downstream speed= 15 + y
Given: Downstream dist/down speed + Up dist/Up speed = 4 hours 10 mins.
[D/S = T, formula used]
30/15+y + 30/15-y = 4 10/60 = 4 1/6 hrs = 25/6 hours
30[(1/15+y) + (1/15-y)] = 25/6
(15 - y + 15 + y)/(15-y)*(15+y) = 25/6*30
30/225-y^2 = 25/180
180*30 = 25*(225-y^2)
[Divide L.H.S & R.H.S by 25]
216 = 225 - y^2
y^2 = 9
y = 3 km/hr
Hence, speed of flow of water = 3 km/hr.
Hope it helps
Similar questions