Question 17610
Let the speed of the plane in still air be x mph
Let the speed of the wind be y mph
<br>
Then in the first case,
x+y=the total speed
total speed=total distance/total time
=100/1
=100 mph
<br>
x+y=100
<P>
Now in the second case,
x-y=second speed
second speed=same distance/more time
=100/(1+40/60)
=100/(1+2/3)
=100/(5/3)
=60 mph
<br>
x-y=60
<P>
Now we have two equations
x+y=100
x-y=60

adding the two,
2x=160
x=80 mph
<br>
y=100-x=100-80=20 mph
<P>
Therefore,speed of wind=20 mph and speed of plane is 80 mph
Hope this helps,
Prabhat