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