Question: So i want 12.6666667 to show up as 12.6 and not 13 or 12.67
This is what i have done

```
Math.Round((5 * (53 - 32)) / 9, 1)

```

Answer: 
```
d -= d % 0.1; //Where 0.1 is the desired least significant unit.

```

It should truncate rather than round at whatever precision you would like, and it seems to work fine on negative numbers as well, always rounding towards zero.
If you want 12.6666667 to show up as 12.6, you'll have to truncate, not round; otherwise you'd get 12.7 to one decimal place.

Personally I'd do that by going ((int) (12.6666667 \* 10)) / 10.