Self-described ``photo-illustrator'' McMillan ( Mary Had a Little Lamb ; One, Two, One Pair! ) continues to focus his talents on the concept picture book--and once again brings his fresh perspective to this sometimes didactic genre. In this ingenious combination of fractions and food a perky pair of budding mathematicians, boy and girl, divide a series of foods into halves, thirds and quarters. After each division they (sometimes with help from a hungry dog) delightedly devour the whole thing. These kids, though obviously posed for the photos, seem to be really enjoying themselves; their pleasure and zest is contagious in the bright, almost shadowless images. Math was never so much fun or so wholesomely delicious. Recipes and suggestions for how children can use their new math skills to measure ingredients and prepare these kid-tested treats are included. Ages 4-8.