<PRE><B>Question 159809</B>
A 6-passenger plane cruises at 180 mph in calm air. If the plane files 7 miles
 with the wind in the same amount of time as it flies 5 miles against the wind,
 then what is the wind speed?
:
Let x = wind speed
then
(180+x) = speed with the wind
and
(180-x) = speed against 
:
Write a time equation; time = {{{dist/speed}}}
;
With time = against time
{{{7/((180+x))}}} = {{{5/((180-x))}}}
Cross multiply
5(180+x) = 7(180-x)
:
900 + 5x = 1260 - 7x
:
5x + 7x = 1260 - 900
:
12x = 360
x = {{{360/12}}}
x = 30 mph is speed of the wind
:
:
Check solution, find the times at both speeds 210 mph and 150 mph:
7/210 = .033 hrs
5/150 = .033 hrs</PRE>