Year 1 Mathematics · AC9M1N03
Large collections are easier to count when they are partitioned into equal groups and skip counted
Ready to project and teach
Large collections are easier to count when they are partitioned into equal groups and skip counted.
Learning routine: Group equally → Count groups → Skip count → Check total
If the groups are not equal, skip counting gives the wrong total.
Use 10s for big collections, 5s for medium collections, and 2s when pairs are easiest.
Explain your thinking: Say what each part of the model represents, then explain why the answer or conclusion follows.
5 groups of 10 10, 20, 30, 40, 50 total = 50
by 2s by 5s by 10s
Make equal groups Group counters into 5s and skip count to find the total. Model: 5, 10, 15, 20
Check equal Look at groups and decide whether skip counting is safe. Model: 4, 4, 4, 4 = safe
These curriculum examples extend the central model into varied contexts. They are learning contexts, not extra definitions to memorise.
counting a large collection of items using groups of fives or tens and skip counting to work out how many there are; recording the amount and connecting the digits in the number to the grouped materials when using groups of 10
Try and explain: There are six groups of five counters and two loose counters. Count efficiently.
Count 5, 10, 15, 20, 25, 30, then 31, 32. There are 32 counters; the two loose counters are not another group of five.
counting collections of objects such as pencils or images of birds in a tree, by grouping them in tens to enable efficient counting and connecting the digits in the number to the groups of tens and ones
Try and explain: Nine bundles each contain ten pencils, with six loose pencils beside them. What is the total?
96 pencils. Nine tens make 90, and six more make 96.
counting a large collection of Australian \$1 coins by stacking them into piles of 10, skip counting in tens and including any leftover coins to determine the total value
Try and explain: Play money shows four stacks of ten $1 coins and three loose $1 coins. What is the total value?
$43. Count the stacks as $10, $20, $30, $40, then add $3. Each coin is worth one dollar.
Organise a collection into equal groups, then include any objects left over.
A collection has 7 full groups of ten and 4 loose counters. How many counters are there?
Watch for this mistake: Seven groups of ten contain 70 objects, not 7. Remember to include the loose objects after counting the groups.
There are 11 groups of ten and 6 loose blocks. How many blocks?
Count the tens to 110, then the ones.
116 blocks.
A student counts 6 groups of five as 5, 10, 15, 20, 25. What was missed?
Match one number word to each full group.
The sixth group was missed. The total is 30.
Key idea: Large collections are easier to count when they are partitioned into equal groups and skip counted.
Return to the concept model if an answer is uncertain. Use the model to explain, not just to guess.
Use the Practice Sheet for written or hands-on work, Practice for supported feedback, and Test when the student is ready to demonstrate independent mastery.
Large collections are easier to count when they are partitioned into equal groups and skip counted.
Learning routine: Group equally → Count groups → Skip count → Check total
AC9M1N03: quantify sets of objects, to at least 120, by partitioning collections into equal groups using number knowledge and skip counting
Explore optional teaching slide packs for classroom lessons and explanations at home.
Browse Teach & Explain · Browse Print & Go
Teachers: follow SkillrHub on TPT, then email us to request a free sample before buying. Include the year, subject and topic or curriculum code.
After trying the sample, honest feedback is welcome. A TPT review is optional, where available, and does not need to be positive.