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You are given two hourglasses. One measures 4 minutes and one measures 7 minutes. How would you measure exactly 9 minutes?

**Step** | **Time** | **4 minute timer** | **7 minute timer** |

1 | 0 min | Start | Start |

2 | 4 mins | Flip | 3 minutes left |

3 | 7 mins | 1 minute left | Flip |

4 | 8 mins | Stop | Flip (1 minute left) |

5 | 9 mins |
| Stop |

## 3 comments:

This is outright wrong!!

@AliasNeo15 ..tell us correct solution ?

No idea what's going on in your step 4. I don't think it's possible without some working up to the start of the timing:

Start 4 and 7.

Start 4 again when it runs out.

7 runs out, 1m left on 4. Start timing the 9 minutes now.

Just let 4 run out, then run it twice more.

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