Missing Number Problems
Maths: Year 5 & 6 National Curriculum, topic 7.2.1
Writing Missing Number Problems
To work out missing numbers in problems, you can use algebra!
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Turning sentences into algebra
- You can turn sentences into algebra.
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Solving algebra
- To solve something in algebra means to find the number that should go instead of the letter to make the equation work.
- In this example, n = 13.
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Example 2
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Example 3
Missing Number Problems
You can use missing number problems to find missing numbers in examples in real life.
Example
- I am making a cake.
- The weight of the cupcake case is 12 g.
- Each cupcake case is filled with different amounts of cake mixture (c).
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The missing number problem
- The expression to solve this problem is 12 + c = w.
- 12 is the weight of the cupcake case.
- c is the weight of the cake mixture.
- w is the weight of the cupcake.
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Substitution
- You can work out the missing values in the table by substituting the values into you know into 12 + c = w.
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Weight of mixture = 324 g
- 12 + c = w
- 12 + 324 = w
- w = 336 g
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Weight of cupcake = 356 g
- 12 + c = w
- 12 + c = 356
- c = 356 − 12
- c = 344 g
Test yourself on Missing Number Problems
What is the algebraic formula for the weight of a plant pot with soil?
What is the algebraic formula for the weight of a bucket with sand?