How to use scss variable in calc?

Question

Sass

Hello, please tell me why this code does not compile correctly

div {
  $item-margin: 1vmin;
  width: calc(50vw - $item-margin * 2);
  height: calc(50vw - $item-margin * 2);
  background: red;
}

output only

div {
  width: calc(50vw - $item-margin * 2);
  height: calc(50vw - $item-margin * 2);
  background: red;
}

Answer 1

div {
  $item-margin: 1vmin;
  width: calc(50vw - #{$item-margin} * 2);
  height: calc(50vw - #{$item-margin} * 2);
  background: red;
}