Question

A boat takes two hours to travel 8km down and 8km up the river when the water is still how much time will the boat take to make the same trip when the river starts flowing at 4km/hr??

Answer 1

Heya!!!

☆ Here's ur answer ☆

Time=distance/velocity
Vbr= 8km/hVrg=4km/h
Let t1 and t2 be the time taken by boat to travel in upstream and downstream respectively Upstream=8-4=4
Downstream=8+4=12
T1=8/4=2hr
T2=8/12=2/3
Total time=2+2/3=2 hr and 40 mins

☆Hope it helps ☆

Answer 2

Given:
Boat can go 8km upstream in 1 hr
And 8km downstream in 1 hr

Velocity of boat in still water = 8km/h

V1 = Velocity of boat w.r.t to river = 8km/hr
V2= Velocity of river w.r.t to ground = 4km/hr

Down speed velocity of boat =
(8+4)km/h = 12km/hr

Upstream speed velocity of boat =
(8-4)km/hr = 4km/hr

Time taken down speed = 8/12
Time taken upstream =8/12 + 8/4

= 2/3+2
= 2+6/3
= 8/3
= 2.66 sec

Therefore, time taken by boat to make the same trip when river starts flowing at 4km/hr is 2.66 sec.
$hope \: it \: helps \: you.$