Ahoming device left its home to deliver a message. on takeoff, the device encountered a tailwind of 14 mph and made the delivery in 5 minutes. the return trip into the wind took 10 minutes. how fast could the device fly in still air?

speed in still air is 42 mph

Explanation:

given data

tail wind speed = 14 mph

time t1 = 5 min = 5/60 hr = 1/12 hr

return time t2 = 10 min = 10 /60 hr = 1/6 hr

to find out

how fast they fly

solution

we consider here speed in still air is x

then

speed in wind will be = x + 14

and against wind speed = x - 14

so

distance = speed × time   1

so in wind distance = ( x + 14 ) × 1/12    2

and against wind distance = ( x - 14 ) × 1/6    3

so from equation 2 and 3

( x + 14 ) × 1/12 = ( x - 14 ) × 1/6

x = 42

so speed in still air is 42 mph