I think you mean question 5. (c) from the 1992 paper... is this it?-
A timber worker was stacking logs. The logs are stacked in layers, where each layer contains one log less than the layer below. There are 5 logs in the top layer, six logs in the next layer, and so on. There are n layers altogether.
(i) Write down the number of logs in the bottom layer
(ii) Show that there are 1/2n(n+9) logs in the stack.