SOLUTION: Against the wind a commercial airline in South America flew 840 miles in 4 hours. With a tailwind the return trip took 3.5 hours. What was the speed of the plane in the air? What w

Question 985097: Against the wind a commercial airline in South America flew 840 miles in 4 hours. With a tailwind the return trip took 3.5 hours. What was the speed of the plane in the air? What w
Answer by ikleyn(52791)   (Show Source): You can put this solution on YOUR website!

Let u be the plane speed in the still air (in miles per hour) and let v be the wind speed (also in ).
Then the speed of the plane against the wind is u - v (relative to the earth), while the speed with the tailwind is u + v.

Thus you have the system of two equation for two unknowns

,

or, dividing the first equation by 4 and the second equation by 3.5

.

Add the equations in the last system. You will get

2u = 450.

Hence, u = = 225 . It is the speed of the plane in still air.

Next, substitute this value of u into the second equation, and you will get v = 15 for the wind speed.

Answer. The plane speed is 225 in the still air. The wind speed is 15 .

For more wind and current problems see my lessons in this site
    - Wind and Current problems,
    - Wind and Current problems solvable by quadratic equations.

RELATED QUESTIONS
Against the winda commercial airline in south America flew 390 miles in 3 hours. with a... (answered by josmiceli)

Against the wind a commercial airline in South America flew 588 miles in 3.5 hours.With a (answered by Alan3354)

Against the wind a commercial airline in South America flew 784 miles in 4 hours. With a (answered by Alan3354,ikleyn)

Against the wind a commercial airline in South America flew 450 miles in 3 hours. With a... (answered by scott8148)

against the wind a commercial airline in south america flew 420 miles in 3 hours. with a... (answered by mananth)

Against the wind a commercial airline in South America flew 480 miles in 3 hours. With a... (answered by josgarithmetic,MathTherapy,Alan3354)

Against the wind a commercial airline in South America flew 540 miles in 3 hours. With a (answered by ikleyn)

Against the wind a commercial airline in South America flew 360 miles in 3 hours.... (answered by josgarithmetic,josmiceli)

Against the wind a commercial airline in South America flew 340 miles in 2.5 hours With a (answered by mananth)