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a motorcycle driver 15 kph faster than a bicycle rider. the motorcycle driver covers 60 km in two hours less than the time it takes the bicycle rider to travel the same distance. what could be the mathematical equation to this and in solving it?


Sagot :

let x = speed of motorcycle 
    y = speed of bicycle
    z = time for the bicycle to travel 60km

y km/hr  + 15 km/hr = x km/hr 
60 km = y km/hr * z hr
60 km = x km/hr * (z-2) hr

y + 15 = x ----->(eq 1) y = x - 15
(eq 2)60 = zy     ----->(eq 3) 60 = (x-15)z   ----> (eq 4) z = 60/(x-15)
60 = xz - 2x  -----> 60 = x (60/(x-15)) -2x

60 + 2x = 60x / (x-15)
60x - 900 + 2x^2 - 30x = 60x
2x^2 -30x -900 = 0
x^2 - 15x - 450 = 0

(x-30)(x+15) = 0
x=30km/hr

using eq 1:
y = x - 15
y = 30 - 15
y=15km/hr

using eq 2:
60 = zy
60 = z (15)
z = 4 hr

(30,15,4)