Starter quiz
This picture has been represented with the equation 2 + 5 = 7 Which number must be subtracted to undo the change?- 2
- 5 ✓
- 7
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- Match the addition equations to the inverse equation.
- 6 + 2 = 8⇔8 − 2 = 6 ✓
- 2 + 6 = 8⇔8 − 6 = 2 ✓
- First, there were 8 cakes on my plate. Then, 3 cakes were eaten. Now, there are 5 cakes on my plate. Write the equation which would undo the change made in this story?
- '5 + 3 = 8' ✓
Look at the picture. Which of the following represents the story?- Which equation would undo the addition 5 + 1 = 6
- 1 + 5 = 6
- 6 − 1 = 5 ✓
- 6 − 5 = 1
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- Which equation would undo the subtraction 9 − 5 = 4
- 5 + 4 = 9
- 4 + 5 = 9 ✓
- 9 − 4 = 5
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Exit quiz
Aisha picks up 4 beads. First, she picks up 3 white beads. Then, she picks up 1 red bead. She represents this with this equation 3 + 1 = 4 What subtraction equation would she write to undo this?- '4 − 1 = 3' ✓
What amount will make this representation correct? What number is missing from the number line?- '4' ✓
Alex collects some conkers. First, he puts 6 conkers in his pocket but then 5 conkers fall out. Now, he has 1 left. 6 − 5 = 1 Which equation would undo this change?- 5 + 1 = 6
- 1 + 5 = 6 ✓
- 6 − 1 = 5
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Which pair of equations are being shown in this picture?- 5 − 4 = 1 1 + 4 = 5
- 4 − 3 = 1 1 + 3 = 4
- 4 − 1 = 3 3 + 1 = 4 ✓
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Aisha and Alex are telling their own 'First, then, now' stories for this picture. Who is correct?- Aisha says, "First I had 3 cubes. Then Alex gave me 6 more. Now I have 9 cubes."
- Alex says, "First I had 9 cubes. Then I gave 6 to Aisha. Now I have 3 cubes."
- Both Alex and Aisha are correct. ✓
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I created a picture to show a 'First, then, so, then, now' story. How much was added to the amount at the start of the story?- 3 pounds ✓
- 1 pound
- 4 pounds
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Worksheet
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Video
Lesson Details
Key learning points
- Addition is the inverse of subtraction. Addition can 'undo' subtraction.
- Subtraction is the inverse of addition. Subtraction can 'undo' addition.
- When an amount is added to the start of a story, to 'undo' the change we must subtract the same amount.
- When a given amount is subtracted from the start of a story, to 'undo' the change we must add the same amount.
Common misconception
Children may look at the numbers but not be able to visualise the context, for example, they may try to undo 6 + 4 = 10 with 10 - 6 = 4
Use practical equipment to illustrate the importance of the number added and subtracted being the same. Link equations to contexts ensuring that children are secure with what each part of an equation represents when linked to a story context.
Keywords
Add - o find the total, or sum, by combining two or more parts (addends), or to increase an amount by adding another.
Subtract - To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.
Inverse - Inverse means the opposite in effect; the reverse of.
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