How to calculate percentages in LESS CSS?

Question

I would like to calculate the width of child-container (div etc) in percentages depending on the parent container with LESS CSS.

I am using the forumula by Ethan Mar

Answer 1

Maybe the percentage function didn't exist when OP was asking but for future reference I add this answer.

div.child-container {
    width: percentage(140/620);
}