George walks 1 mile to school. He leaves home at the same time each day, walks at a steady speed of 3 miles per hour, and arrive
s just as school begins. Today he was distracted by the pleasant weather and walked the first 12 mile at a speed of only 2 miles per hour. At how many miles per hour must George run the last 12 mile in order to arrive just as school begins today?
Note that on a normal day, it takes him <span>1/3</span> hour to get to school. However, today it took <span><span><span>1/2 mile </span><span>2 mph</span></span>=1/4</span> hour to walk the first <span>1/2</span> mile. That means that he has <span>1/3−1/4=1/12</span> hours left to get to school, and <span>1/2</span> mile left to go. Therefore, his speed must be <span><span><span>1/2 mile</span><span>1/12 hour</span></span>=<span>6 mph</span></span>, so 6 is the answer.
