Math question involving D=RT

Question

the question is:

 

A jet flies 3 hours west with a 70mph tailwind. Returning against the wind takes 4 hours. Find the speed of the jet with no wind.

 

What is the best method to solving this?

Answer 1

Hey Ninos,

 

First, remember that distance D is a constant, so you don't need to know what it is to begin. Just equate the outgoing trip's distance Dwith the return trip's distance D and you can proceed.

 

Let x = jet speed in no wind. Thus speed of jet going west is x + 70, and coming back it's x - 70. Since the distance is the same, you can write

 

3 hours * (x + 70) miles/hour = D = 4 hours * (x - 70) miles/hour.

 

That is, for simplicity, 3(x+70) = 4(x-70).

 

Solve for x and you're done.

 

Eric Moline