Help on last question!?

Question

im on my last problem and i keep messing up

you drive home steadily at 65 mph for 130 miles, then slow down to 55 mph. you arrive home after 3 hrs 20 min. how far was the distance you drove and what was the average speed?

Answer 1

65mph for 130 miles=> you drove for 2hours

distance travelled in the rest 1 hr 20 min =55 X 4/3 hrs=73m approx

total distance=130+73

avg speed=total distance/total time

Answer 2

So first you need to know the formula of speed:

Simple speed formula:  s = d/t

You are given the values for s and d, s = 65 and d = 130

so:  65 = 130/t

t = 130/65

t = 2 hours. ---> This means that it took you two hours before you slowed down to 55mph

Which also means that for the second part of your trip, you have these given: s = 55mph and t = 1hr and 20 min. or 1.33 hr or 4/3 hr

How 4/3 hr came to be:

Since you already took 2 hours before slowing down, you only have one hour and 20 min more to finish the trip. Meaning after you slowed down, it took you 80 min. to get home. Now, since we are using the unit "hour", we need to convert 80 minutes into hours. If you try to convert that, you would end up with 1.3333333333 or in fraction terms, 4/3..

Going back, you now have s and t, s = 55mph and t = 1.33. To find the distance:

s = d/t

55 = d / 1.33

55(1.33) = d

d = 73.33 miles

To compute for the average speed, all you need to do is add the two given speed and divide the answer by two. The final answer will be: 60mph..