Question 913547

Plane flies from Det. to Den. it has to fly against the wind and takes 8 hours. On return it goes with wind takes 7 hours. If distance between Det. and Den. is 1120 miles what as speed of the airplane in still are ? What was speed of wind ? 

1120=8p-8w   
1120=7p+7w

p represents plane w wind I got this far and am confused since I
cant substitute ?
<pre>
Let speed of airplane in still air, be S, and wind, W
Then, "against the wind equation" is: {{{S - W = 1120/8}}}_____{{{S - W = 140}}} ----- eq (i)
"With the wind equation" is: {{{S + W = 1120/7}}}______________{{{S + W = 160}}} ----- eq (ii)
2S = 300 ------ Adding eqs (i) & (ii)
S, or speed of airplane, in still air = {{{300/2}}}, or {{{highlight_green(150)}}} mph
150 - W = 140 ------- Substituting 150 for S in eq (i)
- W = 140 - 150
- W = - 10
W, or speed of wind = {{{(- 10)/(- 1)}}}, or {{{highlight_green(10)}}} mph