Year 1: Balance scales and counting cubes
Part of the Year 1 mass and capacity chapter. Chapter overview · whole chapter on one page · Download worksheet (PDF) · Answers (PDF)
Balance scales and counting cubes
A balance scale can show how heavy things are. Put an object on one pan. Add cubes to the other pan, one at a time, until the scale is level.
Then count the cubes. The number of cubes tells us how heavy the object is. Cubes are a non-standard unit. We use them to measure because we can count them.
Key ideas
- A balance scale is level when both sides weigh the same.
- We measure how heavy something is by counting cubes.
- The cubes must all be the same size.
- The number of cubes is the weight in cubes.
Key words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the book and the scale. When the beam is level, both sides weigh the same.The book weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2, 3, 4, 5
- Write the answer. The last number is how many cubes there are.5 cubes
Check. Take one cube away. The scale tips, so 5 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Key words. More means a bigger number. Take away to find out how many more.
Method. Find how many more. Take the smaller number away from the bigger number.
- Count the cubes for each. Use the numbers you counted.brick: 8 cubes, book: 5 cubes
- Take the smaller number away. What is left is how many more.8 − 5 = 3
- Write the answer. 3 more cubes
Check. Add them back: 5 + 3 = 8. ✓
Watch out. Start with the bigger number and take the smaller one away.
Method. Count the cubes on each scale. Then choose the one that needs more cubes.
- Count the cubes for A. Each cube is one unit.A: 3 cubes
- Count the cubes for B. Each cube is one unit.B: 2 cubes
- Compare the two numbers. The bigger number is more cubes.3 > 2
- Write the answer. A (the ball)
Check. 2 is smaller than 3, so the answer is right. ✓
Watch out. Count the cubes on both scales. Do not guess from the size of the objects.
Watch out
Watch out: every cube must be the same size. If one cube is bigger, the count will be wrong. Count each cube only once.
Exam tip
Grown-up tip. Use a kitchen balance or a simple DIY scale with two bowls, and small toy bricks or coins as cubes. Ask: “How many bricks balance the apple?” Let your child move the bricks and count.
Exercise 8B Counting cubes on a balance
Non-calculatorKey words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the apple and the scale. When the beam is level, both sides weigh the same.The apple weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2
- Write the answer. The last number is how many cubes there are.2 cubes
Check. Take one cube away. The scale tips, so 2 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Key words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the ball and the scale. When the beam is level, both sides weigh the same.The ball weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2, 3
- Write the answer. The last number is how many cubes there are.3 cubes
Check. Take one cube away. The scale tips, so 3 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Key words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the brick and the scale. When the beam is level, both sides weigh the same.The brick weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2, 3, 4, 5, 6, 7, 8
- Write the answer. The last number is how many cubes there are.8 cubes
Check. Take one cube away. The scale tips, so 8 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Key words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the bag and the scale. When the beam is level, both sides weigh the same.The bag weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2, 3, 4, 5, 6, 7
- Write the answer. The last number is how many cubes there are.7 cubes
Check. Take one cube away. The scale tips, so 7 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Key words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the apple and the scale. When the beam is level, both sides weigh the same.The apple weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2
- Write the answer. The last number is how many cubes there are.2 cubes
Check. Take one cube away. The scale tips, so 2 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Key words. A balance scale is level when both sides weigh the same. A cube is a unit we can count.
Method. Add cubes to one pan until the scale is level. Then count the cubes.
- Look at the book and the scale. When the beam is level, both sides weigh the same.The book weighs the same as the cubes.
- Count the cubes, one at a time. Touch each cube once so you do not miss one.1, 2, 3, 4, 5
- Write the answer. The last number is how many cubes there are.5 cubes
Check. Take one cube away. The scale tips, so 5 cubes is exactly right. ✓
Watch out. Use cubes that are all the same size. Different sizes give a wrong count.
Method. Count the cubes on each scale. Then choose the one that needs fewer cubes.
- Count the cubes for A. Each cube is one unit.A: 5 cubes
- Count the cubes for B. Each cube is one unit.B: 3 cubes
- Compare the two numbers. The bigger number is more cubes.5 > 3
- Write the answer. B (the ball)
Check. 3 is smaller than 5, so the answer is right. ✓
Watch out. Count the cubes on both scales. Do not guess from the size of the objects.
Key words. More means a bigger number. Take away to find out how many more.
Method. Find how many more. Take the smaller number away from the bigger number.
- Count the cubes for each. Use the numbers you counted.bag: 7 cubes, ball: 3 cubes
- Take the smaller number away. What is left is how many more.7 − 3 = 4
- Write the answer. 4 more cubes
Check. Add them back: 3 + 4 = 7. ✓
Watch out. Start with the bigger number and take the smaller one away.
Key words. More means a bigger number. Take away to find out how many more.
Method. Find how many more. Take the smaller number away from the bigger number.
- Count the cubes for each. Use the numbers you counted.bag: 7 cubes, apple: 2 cubes
- Take the smaller number away. What is left is how many more.7 − 2 = 5
- Write the answer. 5 more cubes
Check. Add them back: 2 + 5 = 7. ✓
Watch out. Start with the bigger number and take the smaller one away.
Method. Look at how many cubes each one balances. More cubes means heavier.
- Sam's bag balances 7 cubes. Use the number of cubes.Sam: 7
- Ruby's apple balances 2 cubes. Use the number of cubes.Ruby: 2
- Compare the two numbers. The bigger number is heavier.7 > 2
- Write the answer. Sam's bag is heavier.
Check. The lighter one balances fewer cubes. ✓
Watch out. Compare the cubes, not the names of the people.
Method. Start with what is already there. Then add the ones you put in.
- Start with 5. That is how many are already there.5
- Add 5 more. Count on from the first number.5 + 5 = 10
- Write the answer. 10 cubes
Check. Take 5 away from 10 to get back to 5. ✓
Watch out. Count on from the first number. Do not start again at one.
Method. The same book needs the same number of cubes every time.
- Look at the two numbers. They should match if both people counted correctly.4 and 6
- Decide if both can be right. The same object cannot need two different numbers of cubes.4 is not 6
- Write the answer. At least one of them has miscounted.
Check. Count the cubes again, one at a time, to find the right number. ✓
Watch out. Check every count. Balance the scale again if you are not sure.
Method. Think about what the count is for.
- Think about the cubes. If one cube were heavier, the count would be wrong.All cubes must weigh the same
- Think about the count. Then the number of cubes tells us how heavy the object is.Count = how heavy
- Write the answer. Each cube must weigh the same, so the count tells us how heavy the object is.
Check. Think about using two different sizes of cube on the same scale. ✓
Watch out. Use cubes that are the same size, every time.