Question 994514
.
t=time; d=distance; r=rate
t=d/r
.
With wind:
t=410mi/r+40
Against wind:
t=310mi/r-40
.
Since time in both directions is the same:
410mi/r+40=310mi/r-40
410(r-40)=310(r+40)
410r-16400=310r+12400
100r=28800
r=288
.
ANSWER: The rate of the plane in still air is 288 mph.