Math Homework help

Question

A plane flies 420 miles with the wind and 350 miles against the wind in the same length of time. If the speed of the wind is 15 ?mph, find the speed of the plane in still air

Answer 1

d=r*t

420=(r+15)t

350=(r-15)t

 

420/(r+15)=t

350/(r-15)=t

 

420/(r+15)=350/(r-15) because they both equal t

cross multiply

420(r-15)=350(r+15)

420r-6300=350r+5250

420r-350r=5250+6300

70r=11,550

r=11,550/70

r=165 mph is the speed of the plane in still air