<PRE><B>Question 1056748</B>
Airplane A travels 2800 km at a certain speed
 Plane B travels 2000 km at a speed 50 km/hr faster than plane A in 3 hrs less time.
 Find the speed of each plane.
:
let s = the speed of Plane A
then
(s+50) = the speed of B
:
Write a time equation, time = dist/speed
A time - b Time = 3 hrs
{{{2800/s}}} - {{{2000/((s+50))}}} = 3
multiply equation by s(s+50), cancel the denominators
2800(s+50) - 2000s = 3s(s+50)
2800s + 140000 - 2000s = 3s^2 + 150s
800s + 140000 = 3s^2 + 150s
0 = 3s^2 + 150s - 800s - 140000
A quadratic equation
3s^2 - 650s - 140000 = 0
You can use the quadratic formula, but this will factor to
(3s+400)(s-350)
the positive solution is what we want here
s = 350 mph for plane A and obviously, 400 mph for place B
and
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