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6.NA.1 – Apply additive and simple multiplicative strategies flexibly to:
6.NA.1.a – Combine or partition whole numbers, including performing mixed operations and using addition and subtraction as inverse operations
Samples: Write numbers – to 100 000. Reading numbers – to 100 000. Comparing numbers – to 100 000.
6.NA.3 – Describe spatial and number patterns, using:
6.NA.3.b – Rules that involve spatial features, repeated addition or subtraction, and simple multiplication.
Samples: Addition two Digit - Missing Numbers. Addition Make 100. Make 100. Challenge puzzle. Addition Of Five Digit Numbers.
Number and place value
ACMNA099 – Use estimation and rounding to check the reasonableness of answers to calculations
Samples: Two digit addition (estimating). Division (estimation) - 1. Rounding numbers to the nearest 10.
ACMNA291 – Use efficient mental and written strategies and apply appropriate digital technologies to solve problems
Samples: Adding on to multiples of 10 - 1. Addition and Subtraction (two step). Addition and Subtraction.
You can go to an overview of all the curricula here.