His grandpa knows why. "Most centipedes have only forty-two legs." (A handy piece of foot-knowledge.) But even so, the centipede soon balks at the morning chore of having to sort out all those shoes and socks, so he flogs them, "to creepy-crawlies with fewer legs". Try it in numeracy hour for number bonds to 100, partitioning of 100 and word problems based on footwear.
Ross fans will also rejoice at the reissue of the Martian-eye view of human life in Dr Xargle's Book of Earthlets, by Jeanne Willis and Tony Ross (Andersen pound;4.99).