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Lisa drove 80 miles, then increased her speed by 20 miles per hour for 180 miles. If the second part of the drive took 1 hour longer than the first part, find her average speed.

a.65 miles/hr
b.43.3 miles/hr
c.52 miles/hr
d.50 miles/hr
e.The correct solution is not shown.

Answer :

E is the correct solution

The average speed is 52 miles/hr, the correct option is C.

What is Speed?

Speed is the rate of traveling a certain distance in a fixed period of time.

It has units of m/sec, km/hr.

Lisa drove 80 miles

Let x hours be the time taken to cover 80 miles

Speed = 80/x

The speed is increased by 20 miles/hour

Speed new = (80/x)+20

Distance covered = 180 miles

Time = x+1 hours

Then,

180/(x+1) = (80/x) +20

By solving this the value of x is obtained

x = 2 hours

Initial Speed = 80/2 = 40 miles/hour

Final Speed = 60 miles / hour

The average speed = Total Distance / Total time = 260/5 = 52 miles/hr

Therefore, the average speed is 52 miles/hr, the correct option is C.

To know more about Speed

https://brainly.com/question/7359669

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