In this activity, we will be working out the missing numbers.
Example 1
In your head, find the missing number.
26 + ? = 50
Answer
Here, it is easy to work out the inverse.
50 - 26 = 24
Example 2
In your head, find the missing number.
-26 + ? = 50
Answer
Here we use the inverse again, but be careful about the negative sign.
50 - -26 means 50 + 26 because two negative signs next to each other make a positive.
50 + 26 = 76
Example 3
In your head, find the missing number.
0.81 + ? = 1
Answer
Here it is easy to work out the inverse - don't be put off by the decimal!
1 - 0.81 = 1.00 - 0.81 = 0.19
It may help to think of 100 - 81 = 19.
Shall we have a go at some questions now?