Average Speed

How would one write a formula to find the average speed if one knows the distance traveled and the rate of speed for each portion of the trip? 20 miles at m speed 40 miles at n speed

Students make the trip to Los Angeles at an average speed of 40mph and the trip back at an average speed of 60 mph. Find their average speed for the entire trip. (It's Not 50 mph) Please help me answer this question and if possible, can you show the steps of solving it. Thank You so much.

Hi everybody. I'm have some trouble with the speed= distance/time. I think It's because it minutes, seconds and fractionsof a second, rather than hours and minutes. 2.8km takes 78.73seconds(1.18.73 ) what is the average speed?

A car traveled 28 miles in 30 minutes. How many miles per hour was it traveling?

A bicyclist rides up a 10 mile hill at a constant speed of 10 MPH. He arrives at the top and heads down to the bottom at a constant speed of 30 MPH What is his average speed for the round trip?