 Grade 2 Font:

# Adding and Subtracting Number to 100

Strand: Number
Outcomes: 8, 9

## Curriculum Focus

This sample targets the following changes to the curriculum:

• The specific outcome in 2007 focuses on demonstrating an understanding of addition and the corresponding subtraction for numbers to 100, using personal strategies with or without manipulatives. The previous mathematics curriculum specified using manipulatives, diagrams and symbols to demonstrate and describe the processes of addition and subtraction. The current reference to "corresponding subtraction" indicates the importance of students' awareness of subtraction as the inverse of addition and the option students have of solving subtraction by thinking addition.
• It is of note that the 1997 curriculum included a specific outcome that stated students should "apply and explain multiple strategies to determine sums and differences on 2-digit numbers, with and without regrouping." This has only changed in the wording "personal strategies," rather than "multiple strategies"; the detailed description of some strategies such as those in specific outcome 6 of Grade 3 gives teachers a clear indication of the kinds of personal strategies that they might expect and structure lessons to encourage.
• The specific outcome in 2007 includes the commutative property of addition and the associative property of addition. The previous mathematics curriculum did not specify these properties at this level. Grade 2 students should recognize that the commutative property does not hold for subtraction.
• The 2007 curriculum specifies the students be able to "demonstrate and explain the effect of adding zero to, or subtracting zero from, any number." Zero is the identity element for addition and subtraction. This was not specified in the 1997 curriculum, although it is an expectation of students.
• The previous curriculum specified that students should have recall of addition and subtraction facts to 10 in Grade 2. There is no mention of an expected time of proficiency with facts to 18 in terms of accuracy and speed. The limitation of addition and subtraction facts being addressed each year (to 10 in Grade 1 and to 18 in Grade 2, with an emphasis on mental mathematics strategies to calculate these), will insure most students either commit them to memory through usage or have efficient ways to calculate them whenever needed.
• The old curriculum heavily emphasized the importance of learning operations in the context of problem solving. Although this is still a component of the new curriculum, it also includes the importance of creating problems to solve.

Adding and Subtracting Number to 100 addresses the following outcomes from the Program of Studies:

Strand: Number
Specific Outcomes:
 8 Demonstrate and explain the effect of adding zero to, or subtracting zero from, any number. 9 Demonstrate an understanding of addition (limited to 1‑ and 2-digit numerals) with answers to 100 and the corresponding subtraction by: using personal strategies for adding and subtracting with and without the support of manipulatives creating and solving problems that involve addition and subtraction using the commutative property of addition (the order in which numbers are added does not affect the sum) using the associative property of addition (grouping a set of numbers in different ways does not affect the sum) explaining that the order in which numbers are subtracted may affect the difference.

## What is a Planning Guide?

Planning Guides are a tool for teachers to use in designing instruction and assessment that focuses on developing and deepening students' understanding of mathematical concepts. This tool is based on the process outlined in Understanding by Design, by Grant Wiggins and Jay McTighe. 