Question

Question #8
& Revis
First 150 miles of his trip, John drove at 50 miles per hour, then due to traffic, he drove at only 20 miles per hour for the next 120 miles. His
average speed, in miles per hour, for the entire trip is​

Answer 1

First 150 miles of his trip, John drove at 50 miles per hour.

$\circ \ {\pmb{\underline{\boxed{\sf{ Time = \dfrac{Distance}{Speed} }}}}} \\ \\ \\ \colon\implies{\sf{ \dfrac{150}{50} }} \\ \\ \colon\implies{\sf{ 3 \ hours}}$

So, John take 3 hours to complete his first trip.

~ Again, He drove at only 20 miles per hour for the next 120 miles.

$\circ \ {\underline{\boxed{\sf{ Time = \dfrac{Distance}{Speed} }}}} \\ \\ \\ \colon\implies{\sf{ \dfrac{120}{20} }} \\ \\ \colon\implies{\sf\purple{ 6 \ hours}}$

this time John take 6 hours to complete his next time.

Now, It's time to find the Average Speed of his whole journey as we know that:-

$\circ \ {\pmb{\underline{\boxed{\sf{ Speed_{(Average)} = \dfrac{Total \ Distance}{Time \ taken} }}}}} \\ \\ \\ \colon\implies{\sf{ \dfrac{150+120}{3+6} }} \\ \\ \\ \colon\implies{\sf{ \cancel{ \dfrac{270}{9} } }} \\ \\ \\ \colon\implies{\underline{\boxed{\sf\large{ 30 }}}}$

Hence,

John's average speed for entire trip is 30 miles per hour.