While teaching a little elementary geometry, this title in the Marilyn Burns Brainy Day series also offers a lesson about fitting square pegs in round holes. Ivan and Alex want to be tailors like their father, but youngest brother Misha dreams of travel. When each son must fashion a cloak for the archduke, Ivan sews one using rectangles of fabric. Alex makes a cloak of squares and an extra cloak of triangles. But Misha's disastrous cloak of circles demonstrates the geometrical concept that shapes must have angles to fit together. Seeing that Misha's heart lies elsewhere, the tailor frees his son to travel the world. As a farewell gift, the tailor presents Misha with the fateful cloak, whose circles he has snipped into snug-fitting hexagons and then restitched. Friedman's story provides an agreeable front for the lesson, and capable watercolors lend a pleasing old-world ambiance. Three pages of clearly written instruction and teaching tips follow the story. Ages 6-9.