15 points!!!!:
Kerri drives $150$ miles to visit her grandmother. She starts off driving $60$ miles per hour, but then encounters road construction and has to drive $20$ miles per hour the rest of the way. If she spends the same amount of time at the faster speed as at the slower speed, then how many hours did her $150$-mile trip take in total?

The formula for speed is speed = distance ÷ time. To work out what the units are for speed, you need to know the units for distance and time. In this example, distance is in metres (m) and time is in seconds (s), so the units will be in metres per second (m/s).

Formula of speed , distance and time

speed = distance ÷ time
distance = speed × time
time = distance ÷ speed

According to the question

Kerri drives 150 miles to visit her grandmother.

i.e

Total distance = 150 miles

She starts off driving 60 miles per hour

First speed (s1) = 60 miles per hour

Then encounters road construction and has to drive 20miles per hour the rest of the way.

Second speed (s1) = 20 miles per hour

Now,

She spends the same amount of time on both speed

Let time taken by individual speed = t

Therefore .

By using distance formula

Distance = speed × time

Distance traveled at First speed (s1)

= 60t

Distance traveled at Second speed (s2)

= 20t

Now ,

Total distance = Distance traveled at First speed (s1) + Distance traveled at Second speed (s2)

150 = 60t + 20t

150 = 80t

t = 1.875 hr

Therefore ,

Total time taken = 2t

= 2 * 1.875

= 3.75 hr

Hence, The total time taken by Kerri to drive 150 miles is 3.75 hr .

To know more about speed , time and distance relationship here:

https://brainly.com/question/10566304

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