Question 405646
D=RT
400=(360+W)T 
T=400/(360+W) FOR THE DOWNWIND FLIGHT.
320=(360-W)T 
T=320/(360-W) FOR THE UPWIND FLIGHT.
BECAUSE THE TIMES (T) ARE EQUAL THEN:
400/(360+W)=320/(360-W)  CROSS MULTIPLY.
400(360-W)=320(360+T)
144,000-400W=115,200+320T
-400W-320W=115,200-122,000
-720W=-28,800
W=-28,800/-720 
W=40 MPH. IS THE WIND SPEED.
PROOF:
400/(360+40)=320(360-40)
400/400=320/320
1/1=1/1
1=1