Balance Scale

The big ideas

What the levels teach, in grown-up words.

• The heavy side goes down. A balance scale compares two things: whichever is heavier pulls its pan down. More of the same thing weighs more.
• Level means equal. When the beam is level, both sides weigh exactly the same. That is what the equals sign means: both sides are worth the same.
• Weigh things with a unit. Counting how many cubes balance a toy gives it a number. Then toys that look very different can be compared and ordered.
• An equation is a balanced scale. 7 = 3 + ? asks how much the right side needs to balance seven. True sentences balance; false ones tip.
• Find the unknown by taking away what you know. If a box and a two balance a nine, the box must be nine take away two. Two equal boxes balancing eight are four each.

Try it at home

Quick experiments that match the game.

1. Hanger scale. Hang a clothes hanger on a doorknob and clip a bag to each end. Put things in the bags and see which side goes down.
2. Weigh in blocks. Use your hanger scale to weigh small toys in building blocks or coins. Write each toy's number and order them.
3. Balance sums. Put 4 and 5 blocks on one side and 9 on the other. Then try 4 and 5 against 8. What happens?
4. Guess the heavier. Hold a shoe in one hand and a book in the other. Guess which is heavier, then check on the scale.