# algebra

• Oct 3rd 2012, 06:44 PM
franios
algebra
an airplane makes a round trip. on the out-leg there is a tailwind of 40 km/hr, while on the return the plane faces a headwind of 40km/hr. if it takes the airplane 4 hours to travel out-leg, and 5 hours to make the return, what is the speed of the airplane in still air?
a) solve this problem

b)solve the problem again, replacing 40km/hr by w, 4 hours by t1, and 5 hours by t2

c)show that the answer to part (b) is proportional to w, and that the constant of proportionality is a function of r=t1/t2

d)graph the answer to part (b) as a function of r (from part (c)), with w=40km/hr and relate the graph to the problem as much as possible. What are the asymptotes, and what do they mean in the original problem?What of the graph is relevant to the original problem ( i.e., what is the domain of r in the original problem)?
• Oct 3rd 2012, 09:55 PM
chiro
Re: algebra
Hey franios.

Can you show us what you have tried? It doesn't have to be a full attempt, but any thoughts you have and any partial attempts will be a good place to start.
• Oct 3rd 2012, 10:34 PM
franios
Re: algebra
For a)(s+40)4=d (s-40)5=d
Then 4s+160=5s-200 doing the algebra we get s=360
Is that correct?
• Oct 3rd 2012, 10:45 PM
chiro
Re: algebra
That looks right. I'm assuming tail-wind "adds" to the speed and the other type "slows it down" and that the distance of both trips are the same. If that's the case then it looks pretty good.
• Oct 4th 2012, 11:01 PM
forumolacabs
Re: algebra
What is the use of "Algebra" in real life?

Airport Drop Bangalore
Bangalore to Coorg
• Oct 4th 2012, 11:03 PM
Prove It
Re: algebra
Quote:

Originally Posted by forumolacabs
What is the use of "Algebra" in real life?

Either as shorthand for writing down a process, or as a means of finding things that are unknown.
• Oct 5th 2012, 09:22 AM
HallsofIvy
Re: algebra
Believe it or not, pilots really do the kind of calculation in this problem- in fact, they do much more complicated calculations, when the wind is NOT in exactly the direction of flight.