Internally the decimal fraction `6.35` is an endless binary. As always in such cases, it is stored with a precision loss.

Let's see:

```js run
alert( 6.35.toFixed(20) ); // 6.34999999999999964473
```

The precision loss can cause both increase and decrease of a number. In this particular case the number becomes a tiny bit less, that's why it rounded down.

And what's for `1.35`?

```js run
alert( 1.35.toFixed(20) ); // 1.35000000000000008882
```

Here the precision loss made the number a little bit greater, so it rounded up.

**How can we fix the problem with `6.35` if we want it to be rounded the right way?**

We should bring it closer to an integer prior to rounding:

```js run
alert( (6.35 * 10).toFixed(20) ); // 63.50000000000000000000
```

Note that `63.5` has no precision loss at all. That's because the decimal part `0.5` is actually `1/2`. Fractions divided by powers of `2` are exactly represented in the binary system, now we can round it:


```js run
alert( Math.round(6.35 * 10) / 10 ); // 6.35 -> 63.5 -> 64(rounded) -> 6.4
```

