title: how to sum input values in angular
body: <p>i create multiple product with increment decrement for quantity like shopping cart...
  i have multiple product list with quantity increment ..i want to sum total qty from multiple products ... how to sum this</p>
  <p><a href="https://i.stack.imgur.com/YNchC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/YNchC.png" alt="enter image description here" /></a></p>
  <p>this is my output:  9</p>
  <p>how to get this in angular</p>
  <p>sum operation only enough for me when click on button</p>