In: Math
A small plane can fly 350 miles with tailwind in 1 3/4 hour. In the same amount of time, the same plane can travel only 210 miles with a headwind. What is the speed of the plane in still air and the speed of the wind?
Answer: Speed of plane in still air is 160 miles/hr and speed of wind=40 miles/hr.
Explanation: Let the speed of plane in still air=u miles/hr and speed of wind=v miles/hr. Since, the time taken during the journey is 1 3/4 hrs. i.e.
hrs.
Distance=Velocity*time. ------------------------------------------------ (1)
The velocity of plane with tailwind=(u+v) miles/hr and velocity of plane with a headwind= (u-v) miles/hr.
Since, with tailwind, the distance travelled is 350 miles. So, using eqn 1.
multiplying both sides by (4/7)
------------------------------------------------- (2)
Since, with headwind, the distance travelled is 210 miles. So, using eqn 1.
multiplying both sides by (4/7)
-------------------------------------------------- (3)
Now, adding eqn 2 and eqn 3
dividing by 2 in both sides
----------------------------------------------------- (4)
So, velocity of plane in still air=u=160 miles/hr.
Now, substitute u=160 in eqn 2, we get.
subtracting both sides by 160
-------------------------------------------------- (5)
So, the velocity of wind=v=40 miles/hr.