## Refresh this page to repeat the challenge |

This exercise reinforces our base ten numeral system. It also helps students compute more accurately and efficiently. Students adding long strings of numbers can group numerals that make 10s to add quickly. Also, students can derive number facts from these facts. For example, if a student knows that 5 + 5 = 10, they can extrapolate that 5 + 7 is 5 + 5 and 2 more so 5 + 7 = 10 and 2 more. |