My trip to work is 120 miles. If I go 8 mph faster than my usual speed, I'll get to work 30 minutes earlier. How long does my trip take, in hours, if I go my usual speed?

Hi, what I have so far are the equations 120=rt and

t-30 = \(\frac{120}{r+8}\)

which equals to \(t=\frac{120}{r+8}+30\)

However, when I plug the expression for the value of t into 120=rt I've gotten answers that don't work. Could someone explain or point out what is wrong? Thanks!

Guest Dec 22, 2019

edited by
Guest
Dec 22, 2019

#2**0 **

You are mixing dimensions...

your rate is in mile per HOUR

your increase in time is in MINUTES.....convert 30 MINUTES to 1/2 hour and resolve for r

120/(r+8) + 1/2 = 120/r

ElectricPavlov Dec 22, 2019