Question

Andy flew his model airplane at full speed straight into the wind for 10 seconds before turning it around and flying with the wind for 5 seconds, again at full speed. The plane flew 50 yards on the way out and 45 yards on the way back. How fast was the wind blowing that day in yd/sec?

Answer 1

what are the answer choices
?

Answer 2

??

Answer 3

A.
2 yd/sec
B.
5 yd/sec
C.
6 yd/sec
D.
7 yd/sec

Answer 4

oki

Answer 5

in general, speed = distance/time

let's let a = the speed of the airplane by itself, with no wind
let w = the speed of the wind

when he flies the airplane into the wind, the wind slows down the airplane. the speed of the airplane is (a - w). the distance is 50 and the time is 10, giving us

(a-w) = 50/10 = 5

for the return trip, he's flying with the wind, so the wind speeds up the airplane. the speed of the airplane on the way back is (a + w). the distance is 45 and the time is 5 giving us:

(a+w) = 45/5 = 9

we want to solve for w, the speed of the wind. subtract the two equations to eliminate a, solve for w.