SOLUTION: Two planes are 2100 miles apart and traveling towards each other. One plane is traveling 80 mi/hr. faster than the other plane. The planes meet in 2.5 hr. Find the speed of the slo

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Question 98923: Two planes are 2100 miles apart and traveling towards each other. One plane is traveling 80 mi/hr. faster than the other plane. The planes meet in 2.5 hr. Find the speed of the slower plane.
Answer by Adam(64) About Me  (Show Source):
You can put this solution on YOUR website!
This is the variation of problem I was already solving. So look at problem 73154 for some info. Anyway, crucial idea - times of flight of both planes are same -) t1=t2 s = v/t v*t=s
v1 = x
v2 = x+80
this is what we substitute into our equations
v1*t=s1
v2*t=s2
s1+s2 = 2100
and get:
x*t=s1
(x+80)t = s2
s1+s2 = 2100
x*t+(x+80)*t = 2100
x*t+x*t+80t = 2100
2xt=2100-80t
2x= (2100-80t)/t
x = (2100-80t)/2t
- (analytic solution)
-
x= (2100-80*2.5)/5
x= (2100-200)/5
x= 1900/5
x= 380 miles/hour