SOLUTION: Johnny gets to work in 20 minutes when he drives his car. Riding his bike (by the same route) takes him 45 minutes. His average driving speed is 4.5 mph greater than his average

Algebra ->  Algebra  -> College  -> Linear Algebra -> SOLUTION: Johnny gets to work in 20 minutes when he drives his car. Riding his bike (by the same route) takes him 45 minutes. His average driving speed is 4.5 mph greater than his average       Log On


   

Question 549928: Johnny gets to work in 20 minutes when he drives his car. Riding his bike (by the same route) takes him 45 minutes. His average driving speed is 4.5 mph greater than his average speed on his bike.
How far does he travel to work?
Answer by mananth(12270) About Me  (Show Source):
You can put this solution on YOUR website!
let the dstance to work be x
speed by bike = y
bike time = x/y = 3/4
x=3y/4
car time = x/(y+4.5) = 1/3
x=(y+4.5)/3
equate both
3y/4 = (y+4.5)/3
cross multiply
9y=4(y+4.5)
9y=4y+ 18
5y=18
y= 3.6 mph
Distance = r*t 3.6 * 3/4 = 2.7 miles (bike)
Distance = r*t 8.1*1/3= 2.7 miles (car)