Starting at home, Jessica traveled uphill to the toy store for 12 minutes at just 10 mph. She then traveled back home along the same path downhill at a speed of 30 mph.
What is her average speed for the entire trip from home to the toy store and back?
cause she used 12 min with 10mph per hour, then we know that she used 30 mph per hour, we can use 12 divide by 3 then we get she spend 4mins in the way back to home. 4+12=16mins 16/60=4/15 （30+10）times 4/15=10.66666....... or 10.7
