You walk one mile to school every day. You leave home at the same time each day, walk at a steady speed of 3 miles per hour, and arrive just as school begins. Today you were distracted by the pleasant weather and walked the first half mile at a speed of only 2 miles per hour. At how many miles per hour must you run the last half mile in order to arrive just as school begins today?
+128475 If you walk at 3 mph then the normal time to make it to school is
(distance) / (rate) = 1 mi / (3mi / h) = (1/3) hr = 20 min
If you walked the first half mile at 2 mph the time it took you is
(1/2)mi /( 2 mi / h) = (1/4) hr = 15 min
Then....you must walk the last 1/2 mile in 5 min = 1/12 hr
So....to find the rate that you must run we have
distance / time = rate
(1/2) mi / (1/12) hr = (12/2) mi / hr = 6 mi / hr = 6mph
