# Upper and lower boundary and logic

In the following skills of upper and lower boundaries which include addition, subtraction, multiplication and division we state that you should use logic.

It's just logic.

But what we mean by that is

Addition | Big number | `+` | Big number | `=` | Biggest number |

Small number | `+` | Small number | `=` | Smallest number | |

Subtraction | Big number | `-` | Small number | `=` | Biggest number |

Small number | `-` | Big number | `=` | Smallest number | |

Multiplication | Big number | `xx` | Big number | `=` | Biggest number |

Small number | `xx` | Small number | `=` | Smallest number | |

Division | Big number | `div` | Small number | `=` | Biggest number |

Small number | `div` | Big number | `=` | Smallest number |

It's obvious. It's logic. Ask yourself what else could it be?