title: Angular concatenating numbers instead of adding
body: <p>Angular typescript concatenating numbers instead of adding</p>
  <p><strong>Class</strong></p>
  <pre><code>  title = 'app';
  
    a: number;
    b: number;
  
    c: number;
  
    calc(): void {
      this.c = this.a + this.b;
    }
  </code></pre>
  <p><strong>View</strong></p>
  <pre><code>&lt;input type=&quot;text&quot; [(ngModel)]=&quot;a&quot; (keyup)=&quot;calc()&quot;&gt;
  &lt;input type=&quot;text&quot; [(ngModel)]=&quot;b&quot; (keyup)=&quot;calc()&quot;&gt;
  
  &lt;p&gt;{{c}}&lt;/p&gt;
  </code></pre>
  <p><strong>Return</strong></p>
  <p>if <code>a = 1</code> and <code>b = 2</code> for example it equal <code>c = 12</code>, it should be <code>3</code> and when i try <code>parseInt(this.a)</code> it result error <code>Argument of type 'number' is not assignable to parameter of type 'string'.</code></p>