Subtraction

Learning Focus/Learning Objectives

Counting Strategies.

(See Mathematics Developmental Continuum Addition and Subtraction Progression Points)

Vocabulary:

Adding, Addition, Counting on, counting up, 100’s chart, open number line, more, less, same, total, sum,

Subtraction, minus, counting back, counting backwards, difference.

 

Warm Up Game

Whole Class Introduction

Student Activity

Share/Reflection

 

5 mins

10 mins

25 - 35

 

Monday

Roll to 0 (100’s Chart)

Check counting on and knowledge of numbers.

Record student understandings.

(Start at 100 and count down)

I went fishing on the weekend with my Mum. We caught 10 but threw 3 back. How many did we have?

Model on 100’s chart, Open # line and # sentence.

You went fishing. How many did each person catch, how many did you throw back and how many fish did you end up with?  P/N/W

Discuss strategies.

How did they use the 100’s chart, Open # line and # sentence.

Tuesday

10 rolls. Highest total wins. Write # sentence.

2+4+1+5......=27

When I opened my bag of lollies last night I counted 15 lollies. My friend ate 6. How many lollies were left?

I bought a bag of 50 lollies. I gave a different amount to each of my family. How many lollies did I have left?  P/N/W

Discuss strategies.

How did they use the 100’s chart, Open # line and # sentence.

Wednesday

Skip Counting.

Around the World. Discuss counting by 3’s. (3,6,9,2,5,8,1,4,7,0)

Play  counting by 3’s until you get around the whole class twice.

My fish tank holds 100 litres. I put 50 litres in my pool and drank 4 litres. How much water was left?

What else could I have used the water for?

How much water was left in your fish tank? Show how much you had and how much you used for each and how much was left for the fish.  P/N/W

Discuss strategies.

How did they use the 100’s chart, Open # line and # sentence.

Thursday

Greedy Pig

I had $25 and gave $5to my brother and $6 to my sister. How much money did I have left?

You had$100 to share with your friends. You gave each person a different amount. How much did you have left?

Draw a table.

Write the number sentence.

Share.

What if there were 1000?

Friday

Roll to 0.

I went to the zoo on the weekend. I counted 37 snakes, then 12 escaped. How many snakes were left?

When you went to the zoo a whole lot of animals escaped. How many were there, how many escaped of each type and how many were left?

P/N/W

Share solutions.

Discuss words associated with subtraction. Create word bank..


Addition and Subtraction - Progression Points

Dimension

level

Progression Point

Number

1.0 Standard

… They use materials to model addition and subtraction of subtraction by the aggregation (grouping together) and disaggregation (moving apart) of objects. They add and subtract by counting forward and backward using the numbers from 0 to 20.

1.25

  • counting forwards and backwards by 1 from starting points between 1 and 100
  • calculation of the next number when asked to add 1 or 2 to any natural number from 0 to 10
  • drawing of diagrams to show subtraction activities

1.5

  • addition and subtraction of two-digit multiples of ten by counting on and counting back
  • counting on from the larger of two collections to find their total
  • use of the number properties (commutative and associative) of addition in mental computation, and recognition of complements to ten; for example, 3 + 4 + 7 + 6 = 3 + 7 + 4 + 6 = 10 + 10 = 20

2.0 Standard

… They add and subtract one- and two-digit numbers by counting on and counting back. They mentally compute simple addition and subtraction calculations involving one- or two-digit natural numbers, using number facts such as complement to 10, doubles and near doubles. They use commutative and associative properties of addition and multiplication in mental computation (for example, 3 + 4 = 4 + 3 and 3 + 4 + 5 can be done as 7 + 5 or 3 + 9).

2.5

  • addition and subtraction of amounts of money including calculation of change from $10
  • use of strategies such as ‘near doubles’, ‘adding 9’ and ‘build to next 10’ to solve addition and subtraction problems
  • use of written methods for whole number problems of addition and subtraction involving numbers up to 99

3.0 Standard

… They estimate the results of computations and recognise whether these are likely to be over-estimates or under-estimates. They compute with numbers up to 30 using all four operations. They devise and use written methods for:

  • whole number problems of addition and subtraction involving numbers up to 999

They devise and use algorithms for the addition and subtraction of numbers to two decimal places, including situations involving money. They add and subtract simple common fractions with the assistance of physical models.

 

4.0 Standard

Students explain and use mental and written algorithms for the addition, subtraction, multiplication and division of natural numbers (positive whole numbers).

Structure

2.5

o        variation of order and grouping of addition (commutative and associative property) to facilitate computations; for example, 3 + 5 + 7 + 5 = 3 + 7 + 5 + 5 = 10 +10 = 20

3.0

They use number properties in combination to facilitate computations (for example, 7 + 10 + 13 = 10 + 7 + 13 = 10 + 20).

4.0

Students recognise that addition and subtraction…are inverse operations.

 


 

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