Mathematics 5 curriculum guide 2015 I table of contents acknowledgements

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MATHEMATICS 5 CURRICULUM GUIDE 2015
Specific Outcomes
ADDING AND SUBTRACTING DECIMALS
Suggestions for Teaching and Learning
Students will be expected to:
Number
5N2 Continued...
5N2.7 Provide a context for when 
estimation is used to:
• 
make predictions
• 
check the reasonableness of an 
answer
• 
determine approximate 
answers
At this point, students should be given problems in which they are 
expected to use reasoning skills to choose the estimating strategy which 
makes the most sense such as:
According to the 
Guinness World Records 2005
TM
, the heaviest head 
of garlic had a mass of 1.191 kg. The heaviest potato had a mass of
3.487 kg. Estimate the combined mass of these vegetables and explain 
the estimation strategy used.
Encourage students to explain, in their own words, why they chose a 
particular estimation strategy. Students should also work with contexts 
which require the addition and subtraction of decimals.
Estimates will give help students make predictions for planning. Angela 
is at the store and sees some flowers that would be perfect in her back 
yard. She knows that the row in her flower bed is 47 cm long. The tag 
on the plants says to plant them 10 cm apart. How many plants does 
she need?
Think: “47 cm is nearly 50 cm, and 50 divided by 10 is 5, so 5 plants 
should be enough.”
Estimates also give students a better sense of the size of answer 
they should get when they solve a problem. Zora wants to buy five 
magazines that cost $1.95 each. When she gets to the check out, the 
amount displayed on the cash register is $12.25. Is that right? Quickly 
estimating how much she expects to pay, she thinks: “Five at $1.95 each 
is about 5 x $2, or about $10 so $12.25 seems too much”.
If a solution differs greatly from the estimate, students should take it as 
a signal to double check their calculations. If you are adding 109 + 56, 
and the calculator shows 75, is that right?
Think: “109 + 56 is close to 110 + 60, which is 170. Ooops! I must 
have punched a wrong number.” In this manner, estimation helps 
ascertain if an answer found through computation is reasonable.
5N2.6 Select and use an 
estimation strategy for a given 
problem.