Emily rode 40 miles at 20 mph to see her cousin. It took her 2 hours. Then, she
left her cousin's to go to the store, another 30 miles away, at 10 mph. It took her 3
hours to arrive at the store. What was the "average speed" for the whole trip?
Ans:
Average speed = total distance / total time taken
Distance to cousin's house = 40 miles
Distance to store from cousin's house = 30 miles
Total distance travelled = 40 + 30 = 70 miles
Time taken to go to cousin's house = Distance / speed = 40 / 20 = 2 hours
Time taken to go to store from cousin's house = 3 hours (already given - even if it is not, the time is distance / speed = 30 / 10 = 3 hours)
Total time = 2 + 3 = 5 hours.
So average speed = = mph.
Hope this helps!