Question

Dave and Sandy Hartranft are frequent flyers with a particular airline. They often fly from City A to City B, a distance of 756 miles. On one particular trip, they fly into the wind, and the the flight takes 2 hours. The return trip, with the wind behind them, only takes1 1/2 hours. If the wind speed is the same on each trip, find the speed of the wind and find the speed of the plane in still air. ​

Answer 1

Answer:

Plane = 441 mi/h; wind =  63 mi/h

Step-by-step explanation:

distance = rate × time

 Let p = the plane's speed in still air

and w = the wind speed . Then,

p + w = speed with wind

 p - w = speed against wind

We have two conditions:

(1)  756 = (p - w) × 2

(2) 756 = (p + w) × 1.5

Distribute the constants                  (3)    756 = 2p - 2w

                                                          (4)   756 = 1.5p + 1.5 w  

Multiply Equation (3) by 3                (5) 2268 = 6p  -  6w

Multiply Equation (4) by 4                (6) 3024 = 6p + 6w

Add Equations (5) and (6)                     5292 = 12p

Divide each side by 12                     (7)        p = 441 mi/h

Substitute (7) into Equation(3)                 756 = 882 - 2w

Add 2w to each side                      2w + 756 = 882

Subtract 756 from each side                    2w = 126

Divide each side by 2                                 w = 63 mph

The plane's speed in still air is 441 mi/h.

The wind speed is 63 mph.

Check:

(1) 756 = (441 - 63) × 2     (2) 756 = (441 + 63) × 1.5

   756 = 378 × 2                   756 = 504 × 1.5

   756 = 756                         756 = 756