Subtraction and Addition Strategies
Students need a range of strategies to work efficiently with numbers. Mental computation strategies are an important building block in mathematics. The following worksheets provide students with opportunities to understand and practise strategies such as rainbow facts, doubles, count on and count back, and bridge to 10.
Rainbow Facts Strategy
Rainbow Facts are number pairs that add to ten. For example: 4+6 and 8+2. Near Rainbow Facts are number pairs such as 7+4 or 5+6. Students can use their knowledge of Rainbow Facts to solve by adjusting up or down 1 as needed. A strong knowledge of these number combinations helps with faster calculation of more difficult number problems.
Having an immediate recall of doubles facts is very important. Doubles can also be used to aid with subtraction. For example: 14-7. Near Doubles Facts are number pairs such as 7+8 or 4+5. Students can use their knowledge of doubles to solve by adjusting up or down 1 as needed.
Count On/Count Back Strategy
Counting on is a very useful strategy when adding 1, 2 or 3 to a given number. Students must identify the larger number and count on to get the answer. Conversely, counting back is used when subtracting 1, 2 or 3 from a given number.
Eg. 3 + 23… 24, 25, 26.
Bridge to 10 Strategy
When adding a number close to 10 (or 100, etc), it can be useful to add as if it were 10 (or 100…), and adjust the answer up or down as needed.
Combination of Strategies
Choose the best strategy to solve the addition and subtraction problems.
Learn and apply different mental computation strategies. Colour the sums according to the strategy used.
Learn and apply different mental computation strategies. Line the sums up to the matching strategies.