The subtitle indicates the book's dual purpose--to entertain and to provide practice in simple addition and subtraction. ""If one fisherman meets one fisherman going to sea, that makes....,"" and so it goes until there are 10 in the boat which inks. Their bizarre rescues involve practice in subtraction. Numbers appear on each page -- spelled out and in bold figure. The illustrations are cartoon figures in black and white, amusing in detail and done with an awareness of the exaggeration-humor of small children. A book both teachers and parents will find useful for the arithmetic-ready.