Chau hiked up a mountain trail and camped overnight at the top. The next day he returned down the same trail. His average rate traveling uphill was 2.2 kilometers per hour and his average rate downhill was 3.3 kilometers per hour. If he spent a total of 13 hours hiking, how long was the trail?

Solution:

                            x/2.2  + x/3.3 = 13

                         5x = 13 * 6.6

                                   x = 17.16 km