WorksheetsAbout this worksheet
In these sums the answer is given and one of the numbers is missing: 7 + __ = 12. The child has to think backwards, which shows whether addition and subtraction, or multiplication and division, are understood as two sides of one fact.
These sheets are also a first step towards algebra. The blank does the job that the letter x will do in later classes.
What this skill is
A missing number sum gives the answer and hides one of the numbers that made it. To solve it the child must use the link between operations: addition undoes subtraction, and multiplication undoes division. Three numbers such as 7, 5 and 12 make a small family: 7 + 5 = 12, 5 + 7 = 12, 12 − 7 = 5 and 12 − 5 = 7.
A worked example
Three blanks, three ways of thinking.
- __ − 5 = 9. Something lost 5 and became 9. Put the 5 back: 9 + 5 = 14.
- 15 − __ = 8. How far is it from 8 up to 15? Count on, or work 15 − 8 = 7.
- 6 × __ = 42. Which number in the 6 table gives 42? 6 × 7 = 42, so the blank is 7.
In each case, put the answer back in the blank and read the whole sum to check it.
Tips for parents and teachers
- Let younger children use counters or fingers to find the missing part, then write it.
- Ask "how did you find it?" The words matter: "I counted on from 7" or "I took 7 away from 12" are both good ways.
- When the blank comes first (__ minus 5 = 9), many children get stuck. Show them that adding the two given numbers finds it.
How to use this sheet at home and in class
- At home: start with "Addition and subtraction" and "Small" numbers. Let the child use beads or buttons for the first sheet and only the mind for the next.
- In class: ask two children to explain how they found the same blank. Hearing a second method teaches more than getting one more answer.
- Use the multiplication and division type as table revision for classes 3 and 4. It is harder to guess than a plain table question.
Mistakes to watch for
- Adding the two numbers that are visible, whatever the sign says. In 7 + __ = 12 the child writes 19.
- Reading the equals sign as "write the answer here" and not as "is the same as". Read sums aloud as "seven and what is the same as twelve?"
- Stopping at the first sum with the blank in the first place. Show that in __ − 5 = 9 the blank is the biggest number of the three.
What to try next
- Simple equations worksheets: the same idea with a letter, for classes 6 to 8.
- Addition worksheets: if the number facts are slow.
- Number sequences worksheets: finding a rule.