Reduce rem by a percentage?

Question

OK I\'m using Foundations rem-calc to calculate a rem value, now i want to reduce the size of the variable on each media query by a percentage like so:

// This          


        

Answer 1

Had to pass the rem-calc after the math like so:

    $herotitle-size: 125.5;

   //To reduce by 10% 0.1
  .hero_home .herotitle{
       font-size: rem-calc( $herotitle-size - ( $herotitle-size * 0.1));
  }