"Double joy" is an original series of books that will turn children's acquaintance with numbers into an interesting game! After all, in addition to the usual illustrations, we have hidden many additional pictures in the booklet. Just turn the page to find them! Playing with the book, the child will easily learn all the numbers from 1 to 10 and will even be able to solve simple arithmetic problems! Wonderful discoveries from this book will make learning a child truly joyful!