Strand: Numbers and Operations
Topic: Whole Numbers
Sub-Topic: Addition

Example/Activity

N-41(h)
38 + 66 + 42 = ___
Think ... take 2 from 42 and add it to 38 to make 40. 40 plus 40 = 80. 80 plus 66 = 146.

N-41(i)
If 24 + 6 = 30 or, if 24 + 6 = 30
then __ + 6 = 40  then 25 + 6 = __
and __ + 6 = 50   and __ + 6 = 41

N-41(j)
18 + 26 + 17 + 5 = __
Think ... 18 + 17 = 35
and 35 + 5 = 40
and 40 + 26 = 66

N-41(k)
43 000 + 45 000 = ______
Think ... 43 + 45 = 88, so 88 000

N-41(l)
26 cm³ + 24 cm³ = __ cm³
Think ... create equal sets to produce two sets of 25 cm³ which equals 50 cm³.

N-41(m)
243 + 65 + 456 + 7 = ___
Think ... Add from the left-most place value - 200, 600, 640, 700, 750, 753, 758, 764, 771.

N-41(n)
274 + 9 = ___
Think ... 273 + 10 = 283
56 + 8 = __
Think ... 54 + 10 = 64

N-41(o)
10 022 fans + 8980 fans = ______ fans
Think ... 10 000 + 9000 = 19 000
Compensate - add 22, subtract 20 = 2
Answer - 19 002

N-42
Can I buy items priced at $29.70, $51.85, $23.17, and $4.50 with a one hundred dollar bill?
If so, how much will be remaining?
e.g., $100.00 - ($29.70 + 51.85 + 13.17 + $4.50) = ______

N-48
You would like to know the approximate cost of new bicycles for yourself and three other family members. You have looked at four of your favourites priced at $188, $147, $224, and $163.
What is the estimated cost of all four bicycles without tax?

N-48(a)
Adding front end digits - Think ... 100 + 100 + 200 + 100 = 500.

N-48(b)
Compensating - Think ... following front-ending I may compensate by adding on 200 to make 700.

N-48(c)
Compatible sets - Think ... 88 plus 24 is about 100. 47 plus 63 is about 100, so 700.

N-48(d)
Special numbers - Think ... values that are easy to compute. 188 and 224 are close to 200. 147 and 163 are close to 150, so 700.

N-48(e)
Clustering - Think ... all numbers are about 200, so 4 x 200 = 800.

N-48(f)
Rounding - Think ... to the nearest $10. 190 + 150 + 220 + 160 = 720.

N-49
You would like to purchase two different outfits of clothes for school. How would you determine the items? The cost? Once your items are chosen, determine whether:

N-49(a)
1. an estimated answer is sufficient.
   N-49(b)
2. using paper and pencil to perform an addition algorithm is necessary.
   N-49(c)
3. an answer can be obtained mentally (use strategies).
   N-49(d)
4. using a calculator is more efficient and/or necessary.

N-50
If all the students in our school could stand head to foot on one another, how high would we reach?
Design a plan to solve.
You may wish to use subtotals for each class.
Estimate before you solve. Is your estimation close to the computed answer? Is your computed answer reasonable?