Jan walks 2 miles at a constant rate of 3 miles per hour and then runs 1 mile at a constant rate of 8 miles per hour.(a) What is Jan’s average speed for the entire trip? (b) Is the average speed in part (a) equal to the average of Jan’s two speeds?
distance / time = average speed
distance = rate * time
time = distance/rate
(2 miles + 1 mile) / (2 miles/3 m/hr + 1 mile/ 8 m/hr)
3 / (2/3 + 1/8) = 3 / (16+3)/24 = 3 * 24/19 = 3.79 m/hr avg
b) no =====> ( 3 + 8)/2 = 5.5 m/hr does not equal 3.79 m/hr
