algebra · Year 5 · Suggested learning sequence
Balance scales and equations
A balanced scale shows two sides with the same mass, just like an equation. You can take the same amount off both sides and it stays balanced. Take off everything beside the boxes until the boxes are on their own. If there are several boxes, share what is left equally between them. If there are boxes on both sides, take the same number of boxes off each side first.
Sample questions
The scale balances. Each small cube has a mass of 1 kg. What is the mass of the box, in kilograms?
- Take 6 cubes off each side, so the scale still balances.
- Now the box is on its own and the right side has 11 − 6 = 5 cubes.
- The box has a mass of 5 kg.
Answer: 5
The scale balances. Each small cube has a mass of 1 kg. What is the mass of the box, in kilograms?
- Take 4 cubes off each side, so the scale still balances.
- Now the box is on its own and the right side has 6 − 4 = 2 cubes.
- The box has a mass of 2 kg.
Answer: 2
The scale balances. Each small cube has a mass of 1 kg. What is the mass of the box, in kilograms?
- Take 1 cube off each side, so the scale still balances.
- Now the box is on its own and the right side has 5 − 1 = 4 cubes.
- The box has a mass of 4 kg.
Answer: 4