Two planes which are 3720 miles apart, fly toward each other. Their speeds differ by 30 mph. If they pass each other in 4 hours, what is the speed of each?

1 Answer
Jun 14, 2017

480 mph and 450 mph

Explanation:

let say thier speed are v_1 and v_2 respectively.
therefore,
v_1 - v_2 = 30 ->i and

v_1 t + v_2 t = 3720

t( v_1 + v_2) = 3720

since t = 4,
v_1 + v_2 = 3720/4 = 930 ->ii

we can find v_1 and v_2 by solving silmutaneos equations i and ii

let say we use eliminate method (i + ii)
2 v_1 = 960

v_1 = 960/2 = 480 mph

replace v_1 = 480 into i,

480 - v_2 = 30

v_2 = 450 mph