title: How to do math on NSNumber
body: <p>I am trying to take a reading off a sensor and display it as a percentage. [some value] will always be between 0 and 1.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>NSNumber *reading = [some value];
  reading = [reading floatValue] * 100;
  </code></pre>
  
  <p>However, I get "Assigning to NSNumber *_strong from incompatible type float"</p>
  
  <p>I am new to working NSNumber objects and struggle to understand how to display my sensor reading as a percentage for the user. Ex: 75% </p>
  
  <p>Thanks for any help</p>