Answers

2014-10-07T20:38:21+08:00
Let 'x' be the speed of one plane
    'y' be the speed of the other planes
since the other is faster than 40mph than the other then we'll have the equation as:
x = y + 40mph  ---equation 1
Note that the given time is 5 hours and that the distance is 2000 mi
distance = speed x time
so we'll have it as:
x(5) + y(5) = 2,000mi
 5x + 5y = 2,000mi  ---- equation 2
substitute equation 1 to equation 2
5x + 5y = 2,000
5(y + 40) + 5y = 2,000
5y + 200 + 5y = 2,000
10y = 2,000 - 200
10y = 1,800
y = 180mph
substitute y=180 to equation 1
x = y + 40
x = 180 + 40
x = 220mph
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