An airplane flew 3.5 hours with a 40 mph head wind. The return trip with a tail wind of the same speed took 2.5 hours. Find the speed of the plane in still air.

Question

mani_jha · Answer

Let the speed of the plane in still air be v.
Speed in the first journey = v+40
Speed in the return journey= v-40
Let the distance be x.
Speed = Distance/Time
You think you can do this now?

anonymous · Answer

lets see...

anonymous · Answer

$$v+40=x/2.5$$
$$v-40=x/3.5$$

mani_jha · Answer

v+40=x/3.5(This is for the first journey)
v-40=x/2.5(This is for the return journey)

anonymous · Answer

v is the speed in still air?

mani_jha · Answer

Yes. Now, can you solve these two equations?

anonymous · Answer

i used elimination and got  v=x/3.5 and v=x/2.5

anonymous · Answer

ok i understand where u r comin from

mani_jha · Answer

@Luis Rivera, shouldnt it be
3.5x-140=2.5x-100
You wrote a + before 100.
@ariesdragon20, follow the method shown by Luis. Did u understand it?

anonymous · Answer

yeah thanks a lot both of you

mani_jha · Answer

Oh ya, you are right. Sorry