Pigs Will Be Pigs: Fun With Math and Money by Amy Axelrod.
This is the first story in a series of books called Pigs Will Be Pigs.
Amy Axelrod wrote these stories as a way to make math more fun and engage children by showing them that math is all around them. She uses real life situations in her stories that children will relate to.
She refers to the Pig Family Moto which is:
Math + Reading = Fun!