Answer:
Let x = speed for the first 96 miles
x - 9 = speed for the last 100 miles
Distance = (rate)(time), so time = (distance)/(rate)
(time for first part of trip) + (time for last part of trip) = 4 hours
So, (96)/(x) + (100)/(x - 9) = 4
Multiply both sides by the LCD (x)(x - 9) to get
96(x - 9) + 100x = 4x(x - 9)
96x - 864 +100x = 4x2 - 36x
4x2 - 232x + 864 = 0
Divide both sides by 4 to obtain x2 - 58x +216 = 0
(x - 4)(x - 54) = 0
x = 4 or x = 54
Note that x can't equal 4 because, in that case, x - 9 would be negative, so x = 54 miles per hour.
Step-by-step explanation:
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