TwiddleLab / Math / Algebra in Motion

Keep It Balanced

Lesson 1 of 12 · 5 min · Free, no account needed

What you will learn

• An equation is a level scale: both sides weigh the same.
• Do the same to both sides and the scale stays level. That's how you solve it.
• The solution is the value that keeps it level: here one bag weighs 3.

Start the lesson

How the lesson goes

1. One bag weighs the same as... what?

   The three bags are identical and the scale is level. Drag the marker to your bet.

2. Take things off. Keep it level.

   Tap a weight to lift it off. Leave only bags on the left, and keep the scale level.

3. Three bags weigh 9. Share the 9 out.

   Every bag weighs the same, so each one gets an equal share.

4. A level scale is an equation.

   Two sides that weigh the same make an equation: 3x + 2 = 11. The letter x stands for the unknown weight.

   Do the same to both sides, and the scale stays level. Taking 2 from both sides gives 3x = 9.

   Sharing both sides by 3 gives x = 3. The value that keeps the scale level is the solution.

5. Make a puzzle for a friend.

   Every bag weighs 4. Put bags and weights on the pans until the scale is level. Put a bag and a weight together on one pan.

6. Game: level up in as few moves as you can.

   A tap lifts an item and its twin off the other pan. When only bags face weights, tap a bag to share.

7. Twist: balloons pull up.

   Each balloon is minus 1, so the left pan is x − 3. Drag weights onto the pans. A weight and a balloon pop together.

Next lesson: Undo, Undo · Part of the course: Algebra in Motion

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