average speed formula problem

 Mathematics Tutor: None Selected Time limit: 1 Day

You drive for 100 miles at 65mph. then you drive for 80 miles at 75mph. What is your average speed for the trip?

Aug 26th, 2015

Thank you for the opportunity to help you with your question!

During the course of my drive, i travel in two successive speeds:

For a distance of S 1=100 miles, the speed of my car is  v 2=65 mph(miles per hour)

This means I took a time of t 1=100/65 h r s. i. e. 20/13 h r s

During second course of my drive:

For a distance of S 2=80 miles, the speed of my car is v 2= 75 miles (miles per hour)

This means I took a time of t 2=80/75 h r s. i. e. 16/15 h r s

Total time taken in the journey=t 1+t 2

= 20/13+16/15

=(300+208)/195

=508/195

=2.605 h r s

Total distance travelled during the journey=s 1+s 2

=100+80 miles

=180 miles

Average speed of my trip= Total distance /Total time

=180/2.605

=69.1 mph

Please let me know if you need any clarification. I'm always happy to answer your questions.
Aug 26th, 2015

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Aug 26th, 2015
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Aug 26th, 2015
May 29th, 2017
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