Edmund's Brainteasers
Problem 5
Solution
Problem 5: Books at the jumble sales. Solution
At the end of each of the December, March and May sales, 15 more books are left than at the previous sale. However, there are 15 fewer at the end of the September sale than at the end of the May sale. Totals at end: September 200, December 215, March 230, May 245. At the following 4 sales there will be 30 more books left at each than in the corresponding sale 12 months earlier. None reach above 300. In the next 4 sales there will be 30 more again. The first sale to have over 300 books left is then that in May 2008 which has 305 books left.