Rodney and Todd are rowing down a river that is 50 yards wide at one end. If the river's width increases from this end uniformly by 2 yards every 10 meters along, and they row along the river at a rate of 5 m/s, how long (in seconds) will it take them to get to the point where the river is 80 yards wide? Think carefully first, then make a decision:
The difference in width between where they're starting from and their destination is 80 - 50 = 30 yards. The width increases 2 yards every 10 m along the river so they would have to cover (30 / 2) * 10 = 150 meters. Traveling at the rate of 5m / s, he will spend 150 / 5 = 30 seconds. So, the answer is 30.