These brightly illustrated books in the Nature Numbers series (4 titles) bring together math activities with facts about animals and the natural world. A Try It! feature on each spread asks a math question loosely based on the content of the page. The mashup is occasionally awkward but more often appealing. How Slow Is a Sloth? focuses on rain-forest creatures and asks readers questions about given measurements, including calculating elapsed time, counting, and working with comparative size. Back matter includes additional activities (not limited to the book's math concept) and answers to the Try It! math questions, as well as a glossary and an index. A fun and unusual take on early elementary math topics for both number and nature lovers.