Therese M. Shea 
Ogres Understand Place Value! [PDF ebook] 

Understanding place value is the key to comprehending large numbers and to learning strategies to easily add and subtract such numbers. Readers will practice place value skills presented by the monsters called ogres. Delightful illustrations and intriguing folklore fact boxes accompany the achievable text. Readers will answer math problems throughout this motivating volume, allowing them to assess their understanding of the critical concepts.