Mathematics 5 curriculum guide 2015 I table of contents acknowledgements

5N2 Use estimation
strategies, including:
• 
front-end estimation
 • compensation
• 
compatible numbers
in problem-solving contexts.
[C, CN, ME, PS, R, V]
• rounding

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49
MATHEMATICS 5 CURRICULUM GUIDE 2015
Suggested Assessment Strategies
Resources/Notes
ADDING AND SUBTRACTING DECIMALS
General Outcome: Develop Number Sense
Authorized Resource
Math Focus 5
Getting Started
Teacher Resource (TR): pp. 8-12
Student Book (SB): pp. 80-81
Lesson 1: Estimating Whole 
Number Sums and Differences
TR: pp. 13-17
SB: pp. 82-85
Lesson 2: Communicating About 
Estimating and Calculating
TR: pp. 18-21
SB: pp. 86-87
Note
Front-end estimation, 
compensation, and compatible 
numbers strategies are located in 
Math Background
in TR: p. 13.
Teachers are encouraged to use 
selected parts of these three 
opening lessons to reactivate 
student knowledge related to 
rounding and estimating with 
whole numbers before extending 
these concepts to include decimal 
numbers.

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50
MATHEMATICS 5 CURRICULUM GUIDE 2015
Specific Outcomes
ADDING AND SUBTRACTING DECIMALS
Suggestions for Teaching and Learning
Students will be expected to:
Number
Achievement Indicator:
5N2 Continued...
Providing opportunities for students to round numbers will help them 
develop skills necessary for using estimation strategies in problem-
solving contexts. Students were introduced to rounding in Grade 3. In 
Grade 5, they will consider to which place numbers should be rounded 
to give the best approximation, and how the strategy of compensation 
may influence the direction in which a particular term may be rounded.
To get a better estimate when adding 10 956 + 2 852 + 13 650, for 
example, if the first two addends were rounded up to the nearest 
thousand, the third could be rounded down to compensate for the high 
estimate of 10 956 and 2 852.
5N2.1 Round decimals to the 
nearest whole number, nearest 
tenth or nearest hundredth.
The following rhyme might be helpful when reviewing the rules for 
rounding. Students should look at the digit to the right of the place 
value under consideration (to which they have been asked to round).
5 or more, let it soar; 4 or less, let it rest.
In Grade 4, students rounded numbers with decimals to the nearest 
whole number. In Grade 5, students should be able to round decimals 
to fewer places such as 2.9286 to 2.9 or 3. The conventions or rules for 
rounding decimals are just like the ones for whole numbers. Rounding 
a number means that you substitute a “friendly” number that is easier to 
use in order to get an estimated anwer.
Decimal 
Nearest 
Thousandth 
Nearest 
Hundredth 
Nearest 
Tenth 
Nearest 
Whole 
Number 
2.9286 
2.929 
2.93 
2.9 
3 
Ask students to suggest situations when it might be useful to round 
decimals. One common example is in describing measurements. A 
wall that is 2.367 metres long, for example, can be estimated as 2.37 
metres or 2.4 m, or as 2 m. Discussion may be warranted regarding 
instances in which each of these rounding choices may be most 
appropriate.

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