Ineed ! answer! first correct answer will get brainliest and i will follow you! you travel along a straight highway, between two cities, 1000 km apart. after leaving the first city and traveling at a constant speed (vs) for a time, you grow tired, stop and rest for 4 hours. after resting, you drive the remaining distance at the same speed as before (vs) until reaching the second city. what is the constant speed you drive at while on the highway (the speed as indicated by the speedometer) in order that the average speed of the entire trip is 65 km/h? (in other words what did the speedometer show while you were driving if the speed was always the same? )

Average speed = (total distance) / (time to cover the distance)

We know:

    Average speed = 65 km/hr
    Total distance = 1,000 km 
    Time to cover it = (Driving Time) + 4 hours.

so we can write:

          65 km/hr  =  (1,000 km) / (Driving Time + 4hr)

          (I'm going to start calling the driving time 'DT'.
           Notice that DT is a number with the units of 'hours'.)

Multiply each side by    (DT + 4hr)

           (65 km/hr) (DT + 4hr)  =  1,000 km   

Eliminate parentheses on the left side:

           (65·DT km  +  260 km)  =  1,000 km

Subtract  260km  from each side:

              65·DT km          =    740 km

Divide each side by 65 :

                DT   =   11.38 hours .

DT (Driving Time) is the time you spent actually driving.
You had to cover the complete 1,000 km in that time.
So while you were driving, you had to do it at a speed of

                  1,000 km / 11.38 hrs  =  87.8 km/hr .


As long as we're already totally bored by this question,
let's work on it some more, and check my

... Driving for 11.38 hours at a speed of 87.8 km/hr, you cover

                     (11.38 hr) x (87.8 km/hr)  =  999.164 km  (close enough to 1,000) .

So far, so good.  The distance is taken care of.

With the 4-hour stop, the total trip takes 4 more hours = 15.38 hours.
So the average speed is

                     (1,000 km) / (15.38 hr)  =   65.02 km/hr

                                                                Close enough to 65 km/hr.  yay !

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