Making suitable choices

Mental computation and estimation is part of everyday life. Facility with this requires:

• a range of mental strategies
• good number sense (working flexibly with numbers and seeing relationships between numbers)
• an understanding of number properties and the relationships between operations.

Developing a 'have a go' attitude encourages students to try different strategies and builds up their confidence.

Present a range of problems, such as:

• 26 \(\times\) 17 =
• 364 ÷ 4 =
• 128 \(\times\) 8 =

Ask students how they might work out the problems mentally. This gives students opportunities to explore a range of strategies without the pressure of having to work out the problems.

Discuss the different ways students might solve a problem. This assists others to expand their repertoire of strategies. For example, to solve 15 \(\times\) 120, a student might think "15  \(\times\) 100 is 1500 and 15  \(\times\) 20 is 300".

Getting a sense of which computations students are comfortable with doing mentally is also valuable. Encourage students to attempt the strategies of others rather than persist with their preferred strategies all the time.

Further exploration of these ideas can be found in the articles Strategies for Going Mental and From Here to There: The Path to Computational Fluency with Multi-Digit Multiplication on the AAMT website.