Do a simple calculation in a mustache.js template

Is it possible to do calculations in mustache.js templates?

I want to multiple a value called ratio by a fixed amount e.g. 240

My tag looks like this:

<div><img src="https://s3.amazonaws.com/com.myapp.demo/{{url}}" class="item" style="height:{{ratio * 240}}"></div>

Since the url value is displayed correctly, I feel it must be the calculation that is causing me trouble.