Mathematics 5 curriculum guide 2015 I table of contents acknowledgements

56
MATHEMATICS 5 CURRICULUM GUIDE 2015
Specific Outcomes
ADDING AND SUBTRACTING DECIMALS
Suggestions for Teaching and Learning
Students will be expected to:
Number
5N2 Continued...
Achievement Indicator:
Compensation is adjusting a computational estimate to make it closer to 
the calculated answer. 
If asked, for example, to estimate the sum
136.2 + 26.2 + 55.2
by rounding or compatible numbers, students might suggest:
140 + 30 + 60 = 230
This results in a very high estimate as, according to the rules of 
rounding, all addends are rounded up. In situations where all addends 
are rounded in the same direction, students could choose to round 
one in the opposite direction in order to improve the accuracy of the 
estimate.
To compensate: 136.2 ( )+ 26.2 ( ) + 55.2 ( ) 
140 + 30 + 50 = 220
This results in a better estimate.
Ask students to think of alternative compensation strategies.
(e.g., 130 + 30 + 60, 135 + 25 + 55) 
Encourage compensation also when all addends would be rounded down 
according to rounding guidelines.
144.95 + 34.89 + 84.5 + 73.09
140 ( ) + 30 ( ) + 80 ( ) + 80 ( ) = 330
5N2.5 Estimate the solution 
to a given problem, using 
compensation, and explain the 
reason for compensation.
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57
MATHEMATICS 5 CURRICULUM GUIDE 2015
Suggested Assessment Strategies
Resources/Notes
ADDING AND SUBTRACTING DECIMALS
General Outcome: Develop Number Sense
Authorized Resource
Math Focus 5
Chapter 2: Lesson 4: Rounding 
Numbers
TR: pp. 29-32
SB: p.p. 50-52
Note
This lesson focusses on estimating 
using rounding of whole numbers.
Additional examples will be 
required to include other methods 
of estimation and estimating with 
decimal numbers.
Interview 
• 
Ask students to answer the following:
Tony has 375 baseball cards and 823 hockey cards. He estimates his
total collection of sports cards to be 1 100. How could he make
his estimate closer to the actual total?
(5N2.5)
Journal
• The fair visited towns all over Newfoundland and Labrador last 
summer. The number of tickets sold for each ride is shown in the 
table below:
Ask students to estimate the total number of tickets sold, using 
compensation. They should explain their thinking.
(5N2.5)
Paper and Pencil
• Joshua told his mom that he will make chili for supper. His recipe 
calls for 0.750 kg of ground beef. All that is left at the supermarket 
is three packages which have masses of 0.157 kg, 0.279 kg, and 
0.381 kg. Ask students to use estimation to determine if he will 
have enough to make his recipe if he buys the three packs. They 
should explain their thinking.
(5N2.5) 
Presentation
• Ask students to estimate and explain their strategy for each of these 
sums.
(i) 346 + 263 
(ii) 952 + 324 + 147
(iii) 75 + 514 + 287 + 22 
They could present one of their answers to a group of classmates.
(5N2.4, 5N2.5))