Jill can't believe it. Her older sister Jenny and older brother Jeff are at it again, arguing over who's got the better backpack and better book. But their biggest battle is over who has the best bedroom in their new house. To measure the area of their windows, they use sheets of paper. Yet even though their windows are different shapes, they both need the same number of sheets—12—to cover the glass. Their windows have the exact same area! Sheets of newsprint come in handy for measuring floor space. Meanwhile, Jill's just happy that her little room is way down the hall.

Understanding that area is a two-dimensional measurement of space is a basic concept of geometry.