Question: Adam has just bought some new books so he has decided to clean up his bookcase. After he adds his new books to his bookshelf he realizes that he has bought enough books to finish completely filling his bookcase with 2 books left over. Before his shopping trip, Adam had 56 books in his bookcase. If his bookcase has 4 shelves and averages 20 books per shelf, how many books did Adam buy on his shopping trip? Think carefully first, then make a decision:
Adam's bookshelf has 4 shelves that fit 20 books each, which is 4 * 20 = 80 books in total to fill the bookshelf. Adam ended the day with a full bookcase of 80 books in the bookcase and 2 books left over, 80 + 2 = 82 books total. If Adam started the day with 56 books and ended the day with 82 books then Adam bought 82 - 56 = 26 books bought on his shopping trip. So the answer is 26.