A number of spring picture books add to popular series. Continuing to make arithmetic fun, Math Fables by Greg Tang, illus. by Heather Cahoon, offers 10 rhymes about animals that teach a life lesson while demonstrating basic addition. For the number seven, ""Gone with the Wind"" traces the path of monarch butterflies to Mexico, using every possible combination of addends (5+2; 6+1; etc.): ""Their journey would be very far,/ a thousand miles or more./ The monarchs flew both day and night/ in groups of 3 and 4."" In addition, Tang extends readers' vocabulary (""albeit,"" ""prudent,"" ""sultry""). Cahoon's computer-generated illustrations once again bring personality and charm to the animals and settings.