Most candidates attempted to write down three equations connecting distance and time. The first equation is the equation for the motion of the model aircraft: d T = 5 . The second and third equations represent the vertical and the horizontal motion of the ball. A common error was to write that the ball had travelled a horizontal distance d − 8 instead of 8 d + . The latter is the case because the ball sets off before the aircraft, so must have travelled further. Another common error was to include the 5T in the vertical motion equation, thereby mixing up horizontal and vertical distances. From the three correct equations, the value of T is found by algebraic elimination resulting in a quadratic equation and a single positive solution.