Identify knowns and unknowns in addition equations | Maths

Starter quiz

Which number in this equation is the sum? 100 = 20 + 80
- 100 ✓
- 80
- 20
Which of these are parts in an equation?
- sum
- addend ✓
- difference ✓
- minuend
What is the missing sum in this bar model?
- '180' ✓
What is the value of the missing part in this bar model?
- '120' ✓
What could the missing addends in this bar model be?
- 70 and 70 ✓
- 80 and 40
- 90 and 50 ✓
- 110 and 40
Which equations could be represented by the bar model?
- 260 + 40 = 300
- 260 − 110 = 150 ✓
- 130 + 130 = 260 ✓
- 260 = 360 − 100

Exit quiz

Which number represents the difference in this equation? 25 − 15 = 10
- 25
- 15
- 10 ✓
Match the keywords to their meanings.
- addend
  
  ⇔
  
  A number added to another. ✓
- difference
  
  ⇔
  
  The result after subtracting one number from another. ✓
- sum
  
  ⇔
  
  The total when numbers are added together. ✓
What is the missing part in this bar model?
- '13' ✓
What is the value of the missing part in this bar model?
- '5' ✓
Which pairs of numbers have a difference of 3?
- 17 and 20 ✓
- 22 and 24
- 27 and 24 ✓
- 28 and 30
How could you calculate the missing part in this bar model?
- 415 + 230 =
- 415 − 230 = ✓
- 230 + ___ = 415 ✓
- 230 − 415 =

Worksheet

Presentation

Video

Lesson Details

Key learning points

If the sum is missing, you add the addends.
If an addend is missing, subtract the other addend from the sum to calculate the missing value.
When the numbers are close together, add on to find the difference.

Common misconception

Pupils may confuse the parts and the whole in an equation, especially when there is a missing number.

Bar models are helpful for representing and understanding the parts and the whole. Ensure that pupils understand that minuend and sum both represent a whole. Allow lots of opportunities for pupils to sketch bar models.

Keywords

Addend - An addend is a number added to another.
Sum - The sum is the the total when numbers are added together.
Difference - The difference is the result after subtracting one number from another.