We know that rate of acceleration is constant, which means change of velocity is constant (velocity changes in a linear way). The boat coasted for 11 meters and its speed decreased by 1 m/s. Since deceleration is constant, we can find out how much time the boat spent coasting by dividing 11 meters (distance traveled) by average speed ((2.6+1.6)/2), which gives us 11 /2.1 = 5.238 seconds. The rate of deceleration is change in velocity divided by time. -1 m/s divided by 5.238 seconds = -.19m/s/s.
