Learning Objectives
- Count objects by making groups of 2s, 5s, and 10s
- Understand that grouping makes counting faster
- Count large collections of objects quickly
- Write the total number after counting in groups
- Practise skip counting
Key Concepts
Why Count in Groups?
Counting one by one takes a long time when there are many objects. It is faster to make groups and count. For example, if there are 30 pencils, we can make groups of 10 and count: 10, 20, 30. That is much faster than counting each pencil one by one.
Counting in Twos
When we count in twos, we skip one number each time: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20. This is useful when counting pairs of things like shoes, socks, or gloves. Every pair has 2 items.
Counting in Fives
When we count in fives, we skip four numbers each time: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50. This is useful when counting fingers. Each hand has 5 fingers. Two hands have 10 fingers. Four hands have 20 fingers.
Counting in Tens
When we count in tens, we say: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100. This is the fastest way to count large groups. We make bundles of 10 and count the bundles. If we have 4 bundles of 10 sticks and 3 loose sticks, we have 43 sticks in all.
Grouping and Left Over
Sometimes objects do not divide into equal groups perfectly. If we have 27 marbles and make groups of 10, we get 2 groups of 10 and 7 left over. We write this as 2 tens and 7 ones = 27.
Important Terms
- Group: A collection of objects put together
- Skip counting: Counting by jumping over numbers in a regular pattern
- Pair: A group of exactly 2 items
- Bundle: A group of objects tied or put together, usually 10
- Left over: Objects remaining after making equal groups
Quick Revision
- Counting in groups is faster than counting one by one
- Count in 2s: 2, 4, 6, 8, 10, 12...
- Count in 5s: 5, 10, 15, 20, 25, 30...
- Count in 10s: 10, 20, 30, 40, 50...
- Make bundles of 10 to count large groups quickly
- Objects left after grouping are called "left over"