Mom had gone out with Aurelia and Teresa for the day, to look at wedding dresses. Aurelia and Tom the Lion were actually going to do it! Get married, and I would be invited to the wedding. So today I’d been invited to stay with the Blaines. Josh and I did our algebra homework first. Mr. Hammersmith or The Hammer, as he is known behind his back, always gives us some real brainteasers over the weekends. They’re optional for extra credit. Like this one: It is possible for a set to have no elements. For example, there are no horses 25 hands tall (a hand is 4 inches). Such a set is called a null set, expressed by a pair of empty brackets { }. List ten other examples of a null set. Most of the kids groan but Josh and I both think they are fun to work on. We came up with about thirty examples, like the set of months that begin with the letter K. Or the set of odd numbers exactly divisible by 4. Monday, when kids turn in their answers, The Hammer will hold up the wrong ones and say things like “near-ums don’t count,”
