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WS02 - Trick or treat

Mathematics, Year 2

By the end of Year 2, students order and represent numbers to at least 1000, apply knowledge of place value to partition, rearrange and rename two- and three-digit numbers in terms of their parts, and regroup partitioned numbers to assist in calculations. They use mathematical modelling to solve practical additive and multiplicative problems, including money transactions, representing the situation and choosing calculation strategies. Students identify and represent part-whole relationships of halves, quarters and eighths in measurement contexts. They describe and continue patterns that increase and decrease additively by a constant amount and identify missing elements in the pattern. Students recall and demonstrate proficiency with addition and subtraction facts within 20 and multiplication facts for twos. They use uniform informal units to measure and compare shapes and objects. Students determine the number of days between events using a calendar and read time on an analog clock to the hour, half hour and quarter hour. They compare and classify shapes, describing features using formal spatial terms. Students locate and identify positions of features in two-dimensional representations and move position by following directions and pathways. They use a range of methods to collect, record, represent and interpret categorical data in response to questions.

Number

AC9M2N02

partition, rearrange, regroup and rename two- and three-digit numbers using standard and non-standard groupings; recognise the role of a zero digit in place value notation

Number

AC9M2N04

add and subtract one- and two-digit numbers, representing problems using number sentences, and solve using part-part-whole reasoning and a variety of calculation strategies

Number

AC9M2A02

recall and demonstrate proficiency with addition facts to 20; extend and apply facts to develop related subtraction facts

Annotations

 

1. Formulates the problem situation as an additive number sentence.

 

2. Partitions two-digit numbers into tens and ones, applying knowledge of place value and part-part-whole reasoning.

 

3. Regroups numbers, applying part-part-whole knowledge and addition facts.

 

4. Adds two- and one-digit numbers.

 

5. Solves a subtraction problem involving two-digit numbers, using a diagram and demonstrating knowledge of subtraction facts.

 

6. Partitions a two-digit number into non-standard groupings.

Annotations

 x
1

Represents the problem as addition.

 19 22 15 40
2

Partitions two-digit numbers into tens and ones.

 22 32 15 40
3

Regroups numbers, applying part-part-whole knowledge and addition facts.

 32 53.5 15 40
4

Chooses and applies an additive strategy, demonstrating understanding of the relationship between addition and subtraction.

 58 67 15 40
5

Recognises and represents the problem using subtraction.

 71 87 15 40
6

Uses partitioning to assist with the subtraction calculation.

 88 103 15 40
7

Demonstrates knowledge of subtraction facts to obtain a solution.

 103 108 15 40
Transcript

[Student] First I had

 

[Student] 9 chocolates, 12 lollipops,

 

[Student] and 16 candy canes.

 

[Student] And this is how I sorted it out

to get to the answer

 

[Student] how much I had altogether.

 

[Student] First I split the 12 into 10 and 2,

 

[Student] and the 16 into 10 and 6.

 

[Student] Then I put the 10 and 10 together.

 

[Student] It equaled 20.

 

[Student] Then I put the 6 and the 2 together.

 

[Student] It equaled 8.

 

[Student] Then I put that 20 and the 8

 

[Student] together it equaled 28.

 

[Student] Then I put the 9 in and it equaled 37.

 

[Teacher] Because you know that?

 

[Student] Because I know that 28 and 10 is 38.

 

[Student] Then I took away 1 more.

 

[Student] So he had 50 in the bag first,

 

[Student] then he took away 37

 

[Student] because then he gave 37 to his friends.

 

[Student] So I,

 

[Student] I'm going to take away

 

[Student] 37 and see how much is left.

 

[Student] So first I took away one 10, that equaled 40.

 

[Student] Then I took away another 10, that equaled 30.

 

[Student] Then I took away another 10, it equaled 20.

 

[Student] Then I took away

 

[Student] a 4, it equaled 16.

 

[Student] Then I took away a 3, it equaled 13.