"One lonely guinea pig plus one other lonely guinea pig, make two smiling guinea pigs". One by one, eight more guinea pigs join their friends, adding up to a crowd of ten cavorting guinea pigs and tons of fun! And at the end of the day, the tuckered out youngsters can count on ten of their moms or dads for a great big hug. And twenty guinea pigs are plenty! Kate Duke's irresistible guinea pigs are a delightful introduction to basic addition.