Work Out Missing Numbers

Adding whole numbers means that we are combining numbers to form a total.

Let's say that we had three cards with numbers from 1 to 10 on them and we were told the total of all three numbers added together. If one of the cards was missing its number, how could we work out what it should be?

To identify the missing number on the card,  the sum of the numbers given is subtracted from the total.

Example

Write the missing numbers on the cards.

Method:

6 + 1 = 7

9 - 7 = 2

Answer:

Missing number = 2

Does that make sense?