A boat takes 2 hours to travel 30 km down a river, then 7.5 hours to return. How fast is the river flowing?

Question

A boat takes 2 hours to travel 30 km down a river, then 7.5 hours to return. How fast is the river flowing?
wrong check mark km/hr

Answer 1

river speed = x
dist = 30 = 2* (Vboat + Vriv) = 7.5 * (Vboat - Vriv)
Vb + Vr = 15
Vb - Vr = 4

Vr = 5.5 km/hr

Answer 2

The boat travels at a constant speed with respect to still water of B and the river flows at a constant speed of R. V+ R = 30km/2hrs and V-R = 30km/7.5hrs. Subtracting gives 2R = 30(1/2 - 1/7.5) or R = 15 ( 7.5 - 2)/15 = 5.5 km/hr

Answer 3

Let x be the speed of the river. Let y be the speed of the boat.

When the boat moves down the river, its speed is increased by the speed of the river, and vice-versa.

With that in mind, you have...

(y+x) = 30/2 = 15 km/h

Returning...

(y-x) = 30/7.5 = 4 km/h

Therefore,
y+x = 15, and
y-x = 4

Using simple elimination, you have
2x = 11
x = 5.5 km/h

Answer 4

okay, so you know roudn trip is 60km. Also the boat was going at 15km/h, in total, down the river and 4km/h up the river. Find half the difference between these 2 speeds and you have your answer assuming that the boat is travelling at a constant speed.

(15-4)/2=5.5km/h

so I'm pretty sure that the river flows at 5.5km/h.

Answer 5

First set up equations for the down and up trips. Keep in mind that while going downstream, current will be adding to the speed of the boat and while going upsteam, it will be subtracting. distance=time*speed
30 = 2(boatspeed+current)
30 = 7.5(boatspeed-current)

Solve the first equation for boatspeed:
15 = boatspeed+current
15-current=boatspeed

Substitute boatspeed into the second equation, then solve for current:
30=7.5((15-current)-current))
30=7.5(15-2current)
30=112.5-15current
-82.5=-15current
5.5=current

The river is flowing 5.5km/h downstream.

Good luck.

Answer 6

INSUFFICIENT DATA.... FOR AN ACCURATE..... ANSWER!

WHERE.... are you Flow Measurements of the River and Its Tributaries! Also the Depth and With of Said River....!

Meteorological DATA... is also Missing from your Question!

Where is the DATA..... about Load, Crew, and Cargo Data including Fuel Storage and Fuel Consumption!

Or did you just want..... "A Guss-ta-mate"... and.... NOT an Accurate Answer?

Thanks, RR

Answer 7

I have absolutely no idea, but estimate 5.45 km/hr