Mental maths strategies · Grade 3
In Grade 3 you learn: adding near multiples of 10.
Mental maths is about choosing a clever route through a calculation instead of always using the same written method. Rounding and adjusting, partitioning, doubling and halving, and using facts you already know turn hard-looking sums into easy ones.
Key facts
- Round and adjust: + 99 is + 100 − 1; − 49 is − 50 + 1.
- Double and halve: × 4 is double, double; ÷ 4 is halve, halve.
- Near doubles: 35 + 36 is double 35 plus 1.
Worked examples
Example 1
347 + 199
Answer: 546