Question 582554
It takes Sally three minutes to go one mile with the wind at her back.
 Then it takes her four minutes on the ride back with the wind against her.
 What is the rate of the speed of the wind?
:
Assume they want the speeds in mph
:
Convert 1 mi in 3 min to mph
{{{1/(3/60)}}} = 20 mph effective speed with the wind
and
{{{1/(4/60)}}}  = 15 mph effective speed against the wind
:
Let s = speed in still air
Let w = speed of the wind
:
s + w = 20
s - w = 15
-----------adding eliminates w, find s
2s = 35
s = 35/2
s = 17.5 mph in still air
:
Find the speed of the wind
17.5 + w = 20
w = 20 - 17.5
w = 2.5 mph is the rate of the wind