Gizmo of the Week: Rounding Whole Numbers (Number Line)

The Rounding Whole Numbers Gizmo demonstrates rounding rules with an engaging model of balls rolling down hills. After placing the balls on a flat number line, clicking the “Hill” button causes a hill or hills to form. Balls on either side of the top of the hill roll downwards until they reach a valley that marks a round number. When balls are placed exactly halfway between two round numbers, the ball is carried to the peak of the hill. Students can resolve this ambiguity by clicking Nudge Midpoints, which rounds the numbers up. This Gizmo includes rounding to the nearest tens and the nearest hundreds.