Adding Three Small Numbers
PROCEDURALAdd three one-digit numbers using strategies including looking for pairs that make 10
Mastery Evidence
- Calculate 5 + 7 + 3 by first adding 7 + 3 = 10, then 5 + 10 = 15
- Add any three single-digit numbers correctly
- Identify useful pairs within three addends to make the calculation easier
Assessment Prompt
“If [child] needs to add 4 + 6 + 8, can they spot that 4 and 6 make 10 first, then add 8 to get 18 — rather than just adding in order from left to right?”
Curriculum Standards2 alignments
1.OA.2Common Core State Standards for MathematicsSolve word problems that call for addition of three whole numbers whose sum is less than or equal to 20, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
Maths/Y2/AS/7The national curriculum in EnglandAdd and subtract numbers using concrete objects, pictorial representations, and mentally, including adding three one-digit numbers.
Prerequisites2
- Number bonds to 9softAges 4—6
- Grouping numbers to addhardAges 6—7
Show full prerequisite tree
- Numbers up to 10 into pairs hard
Making 10 is a specific application of decomposing numbers into pairs
- Addition as combining or putting together two hard
Decomposing numbers into pairs requires understanding addition as combining
- How Many in Total? hard
Understanding addition as combining groups requires knowing numbers represent quantities (cardinality)
- One-to-one counting hard
Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
- Addition as combining or putting together two hard
Associativity requires understanding addition as combining
- How Many in Total? hard
Understanding addition as combining groups requires knowing numbers represent quantities (cardinality)
- One-to-one counting hard
Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
- Addition in any order hard
Associative property builds on commutative — both involve rearranging addends
- Addition as combining or putting together two hard
Understanding commutativity of addition requires understanding addition
- How Many in Total? hard
Understanding addition as combining groups requires knowing numbers represent quantities (cardinality)
- One-to-one counting hard
Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'
Unlocks1
- Adding numbershardAges 7—8