The rational number 5/6 is not representable as a binary float. The two nearest binary floats are

```
julia> 7505999378950826/big(2)^53
8.333333333333332593184650249895639717578887939453125000000000000000000000000000e-01
julia> 7505999378950827/big(2)^53
8.333333333333333703407674875052180141210556030273437500000000000000000000000000e-01
```

which reveals that the larger of them is actually closer to 5/6

```
julia> 7505999378950826/big(2)^53 - 5//6
-7.401486830834376936157544453938802083333333333333333333333333045461048163518512e-17
julia> 7505999378950827/big(2)^53 - 5//6
3.700743415417188468078772226969401041666666666666666666666666954538951836481488e-17
```

so this is not a bug. It is the usual issue that humans like decimal numbers but computers prefer binary numbers. Each time a number is read or written there is a conversion happening between the two representations and this is an eternal source of confusion.