Speed Problem Number 2

[susumandrai]

Please guide me in solving these problems. I need to know how to start off:

1. Plane A travels 80km/hr faster than plane B. If plane B takes 33 minutes longer than plane A to complete a journey of 880km, find the speed of plane B.


2. A boat travels at 15km/hr in still water. In travelling 45km downstream from town A to town B, it completes the journey in 75 minutes less than it takes for the return journey. At what speed does the river flow?



3.A man can walk from A to B and back in a certain time at 7km/hr. If he walks from A to B at 8km/hr and returns from B to A at 6km/hr, he takes 2 minutes more. Find the distance between A and B.

 

[susumandrai]

Please guide me in solving these problems. I need to know how to start off:

1. Plane A travels 80km/hr faster than plane B. If plane B takes 33 minutes longer than plane A to complete a journey of 880km, find the speed of plane B.


2. A boat travels at 15km/hr in still water. In travelling 45km downstream from town A to town B, it completes the journey in 75 minutes less than it takes for the return journey. At what speed does the river flow?



3.A man can walk from A to B and back in a certain time at 7km/hr. If he walks from A to B at 8km/hr and returns from B to A at 6km/hr, he takes 2 minutes more. Find the distance between A and B.

All I know is that the answers are like this:
1. 320 km/h
2. 3 km/h
3. 5.6 km

I will be able to do them if someone gives me a start off!

 

[susumandrai]

B speed = b ; then A speed = b + 80
33 minutes = 11/20 hour

880/b - 880/(b + 80) = 11/20 ; solve for b

The other 2 problems are similar...

I have solved the above equation and have realised that it extends to a quadratic equation and thus I have used quadratic formula to find the answer as x = 320.
I believe that this is not a linear algebraic problem and as such cannot be solved using linear equations.
Can anyone confirm to me that this is indeed a quadratic algebra problem!

Well I am still struggling with the last two questions.
I will post if I come up with something......

Thanks for the support

 

[Deleted member 4993]

Yes ... for these problems you'll often get a quadratic equation to solve.

 

[Deleted member 4993]

Please guide me in solving these problems. I need to know how to start off:

2. A boat travels at 15km/hr in still water. In travelling 45km downstream from town A to town B, it completes the journey in 75 minutes less than it takes for the return journey. At what speed does the river flow?

Let the speed of the river = R km/hr

Then

speed of boat up-stream = 15 - R

speed of boat down-stream = 15 + R

Continue....

 

[susumandrai]

Thanks.... i got all questions!