# Tens Complement

**What Makes 10?**

The "Tens Complement" is the number we add to make 10:

Example: The Tens Complement of **3** is **7**, because **3+7=10**

Here are all the Tens Complements:

Number | Tens Complement | Why? Because: |
---|---|---|

0 | 10 | 0 + 10 = 10 |

1 | 9 | 1 + 9 = 10 |

2 | 8 | 2 + 8 = 10 |

3 | 7 | 3 + 7 = 10 |

4 | 6 | 4 + 6 = 10 |

5 | 5 | 5 + 5 = 10 |

6 | 4 | 6 + 4 = 10 |

7 | 3 | 7 + 3 = 10 |

8 | 2 | 8 + 2 = 10 |

9 | 1 | 9 + 1 = 10 |

10 | 0 | 10 + 0 = 10 |

But you only have to remember half the table!

**1** + **9 **= 10 and **9** + **1 **= 10

**1 and 9** are partners!

So are **2 and 8**, **3 and 7**, **4 and 6** and **5 and 5**

## Why is this Important?

Knowing the Tens Complements makes some mental arithmetic a whole lot easier.

For example it is used in Quick Subtraction.

## Practice!

You can practice by using What Makes 10?