David blew his tire and had to drive with a temporary replacement tire for a while. He was not supposed to use that tire to drive long distances or to drive fast, but still he drove to work one day. His average speed going to work was 35 miles per hour and took him about 50 minutes to get there. On his way back home he took a different route; he was going on average at 45 miles per hour and it took him about 45 minutes to complete the trip. How many miles did David drive with this temporary tire? Round your answer to the nearest mile.
I answered 63 and I got it incorrect. This was the explanation:
On the way to work it took him 50/60= 5/6 hours to get there, so he traveled 5/6 x 35 = 29.16 miles. On the way back it took him 45/60 = 3/4 of an hour, so he traveled 3/4 x 45 = 33.75 miles. Thus, David traveled 29.16 + 33.75 = 66.91, which is approximately 67 miles.