You have two containers, one of which will hold three gallons of water, the other five gallons of water. You need exactly four gallons of water. How do you use these two containers to measure out the four gallons? [p. 13) Rachel drives 113 miles from Pittsburgh to Cleveland (two cities in the USA) averaging thirty mile per hour. How fast must she drive on the return trip to average sixty miles per our overall? (p. 19)