Question

The speed of a boat in still water is 15 km/hr.It can go 30 km upstream and return downstream to the original point in 4 hours 30 minutes.Find the speed of the stream.

Answer 1

@Sepeario

Answer 2

if the speed of the stream is v km / hour

speed of boat downstream = 15 + v and upstream speed = 15 - v
distance = speed * time
downstream
30 = t1(15 + v)
upstream
30 = t2 (15 - v)

where t1 and t2 are the times for downstream and upstream

also we have

t1 + t2 = 4.5

Answer 3

so you need to solve the following system of equations

t1 + t2 = 4.5

t1(15 + v) = t2(15 - v)

Answer 4

I'm missing something here as we've got 3 unknown and only 2 equations

Answer 5

sorry i have no time at the moment . Gotta go

Answer 6

\[\frac{30}{15 - v} + \frac{30}{15 + v} = \frac{9}{2} \ [hrs]\]
\[\frac{30(15 + v) + 30(15 - v)}{15^2 - v^2} = \frac{9}{2}\]
\[\frac{2(30)(15)}{15^2 - v^2} = \frac{9}{2}\]
\[2(2)(30)(15) = 9(15^2 - v^2)\]
etc,