Number Trios

If you know an addition fact, you can work out a related subtraction fact. Learning number trios are very useful.

The numbers 11, 4, 7 can be made into these four sums by just swapping the two lower numbers.

4 + 7 = 11               11 - 4 = 7
7 + 4 = 11               11 - 7 = 4

This can be done with many other numbers.

Use your flashcards to play a game. Pick three numbers, two of which add up to the third one. Then try and create four sums using only the plus, minus and equals.

Adding multiple-digit numbers

Written Addition - Carrying on

Sums that are too hard to work out in your head may need to be worked out on paper. Write the sum in columns, lining up the ones, tens, hundreds and so on. Then starting with the lowest place value (on the right), add the digits in each column.

If the number add up to over 10 then write the ones between the lines and carry the tens over to be added with the other tens.