posted by Anonymous .
A Boeing 747 flies 2420 miles with the wind. In the same amount of time, it can fly 2140 miles against the wind. The cruising speed ( in still air) is 570 mph. Find the speed of the wind.
time with the wind = 2420/(570+x)
time against the wind = 2140/(570-x)
but these two times are equal
2420/(570+x) = 2140/(570-x)
1219800 + 2140x = 1379400 - 2420x
4560x = 159600
x = 35
the speed of the wind is 35 mph