An Impossible Task This morning we had a special math test aiming to test students' abstract-thinking ability. One of the problems is to prove a formula, Sn=(a1+an)/2, using the methodology of number-shape combination, for example, the area formula of a trapezoid. The instant I recalled how my physics teacher had proved the displacement formula last year. I drew a trapezoid as she did, and I endeavoured to explain how the rectangles add up to a whole trapezoid. After minutes' hard work, I managed it and went on to the next question. After we handed in the paper, school was already over.I felt content for having finished most of the problems. Nothing was wrong, or at least I thought so, until a boy from the downstairs asked casually if we'd found there was a mistake in the problems - The formula given to be proved was wrong!!! It dropped an 'n'! I was fooled by the wrong formula from the beginning! God knows how I managed to prove it. At least this abdominable problem taught me a lesson: as long as you believe in it, nothing is impossible.