<PRE><B>Question 555059</B>
A plane can travel 350 km/h in still air. With the wind it flew 1000 km.
 In the same amount of time it could travel 750 km against the wind.
 Find the speed of the wind.
:
Let w = speed of the wind
then
(350-w) = effective speed against the wind
and
(350+w) = effective speeed with
:
Write a time equation: time = dist/speed
:
{{{1000/((350+w))}}} = {{{750/((350-w))}}}
Cross multiply
1000(350-w) = 750(350+w)
simplify divide both sides by 250, results
4(350-w) = 3(350+w)
1400 - 4w = 1050 + 3w
1400 - 1050 = 7w + 4w
350 = 7w
w = {{{350/7}}}
w = 50 mph is the speed of the wind
:
:
Confirms this find the times of each trip
1000/400 = 2.5 hrs
750/300 = 2.5</PRE>