# Rate Calculations

A rate is a quantity of one unit in relation to another

```
3 hours / day | 3 hours/day
$99 per week  | $99.00/week
```

Soulver also supports rates with no unit

```
30 bottles / week  | 30/week
30/week as / month | 130/month
```

You can add/subtract rates

```
$20/day + $300/week | $440.00/week
```

And convert them into other compatible forms

```
€30/day in €/month | €913.11/month
```

A simplified rate is also produced from a division of units of different kinds:

```
90 km / 3 day | 30 km/day
```

{% hint style="info" %}
Mathematics requires that units of rates in the same unit category cancel each other out when dividing:

3 hours / 3 days = 0.0416667

This is essentially the first number as a proportion of the second number (10,800 s / 259,200 s), expressed as a decimal.

It can be more helpful to simplify the rate without cancelling units. If you would rather express the proportion as a simplified rate, you can specify the format explicitly:

3 hours / 3 days as hour/day = 1 hour/day
{% endhint %}

### Multiplying rates

```
$50/week × 12 weeks  | $600.00
$24 a day for a year | $8,765.82
500/day to / year    | 182,621.25/year
```

### Handy rate-related phrases

Here are some convenient built-in phrases for doing calculations with rates

```
30 hours at $30/hour | $900.00
$500 at $20/hour     | 25 hours
```