# why we use computers

When we think about what computers do, math, we can reason about why they are used. How long does it take you to add or subtract a number?

method | time | year invented |
---|---|---|

by hand | less than 1 operation per second | |

US Navy ENIAC computer | less than 5000 operations per second | 1943 |

a laptop | 166,080,000,000 operations per second | 2018 |

Summit super computer at oak ridge national lab | 1,000,000,000,000,000, operations per second | 2018 |

## So it’s because they’re fast?

Yep, pretty much. This allows us to do things that would be otherwise impossible to do by hand.

What’s that mean? Some of the problems that computers solve would take longer than our lifetime to compute.