A scale has 90cm and 100cm long arms, if we place 100kg on 90cm what weight should we need to put at 100cm arm to balance the scale?

A scale has 90cm and 100cm long arms, if we place 100kg on 90cm what weight should we need to put at 100cm arm to balance the scale?

Explanation

A scale has 90cm and 100cm long arms, if we place 100kg on 90cm, 90kg weight should we need to put at 100cm arm to balance the scale