Question 89115
Let the speed of the plane = S
Let speed of Wind = W

Now speed of plane per hour = 1240/4 = 310
Since the tail wind aids the plane S+W = 310

Similarly S-W = 1500/6 = 250

S+W = 310
S-W = 250
Adding both
2S = 560
S = 280

Therefore speed of plane = 280