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Lecture

# Lecture 5

School
UOIT
Department
Education
Course Code
CURS 4240U
Professor
Ann Le Sage

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October 2, 2012
Different methods to do mental math --> 114 + 69
o Do it in pieces
100 +69 = 169 169
169 + 10 = 179
179 + 4 = 183
*importance of place value
Using fingers to count = good thing!
o 70 + 100
170 + 10 = 180
180 + 4 = 184
184 - 1 = 183
(done vertically) --> add 1 to make it a "friendly number" and then subtract 1 at
the end
o 114 + 69
4 + 9 = 13
110 + 60 = 170
13 + 170 = 183
o 114 + 69
114 = 100 + 10 + 4
69 = 70 - 1
100 + 70 = 170
170 + 10 = 180
180 + 4 = 184
184 - 1 = 183 183
o 114 + 69
4 + 9 = 13
1 + 6 = 7
100 + 70 + 13 = 183
*place value vs. face value -> 1 + 6 vs. 10 + 60
Face value -> 7; vs. place value -> 70
o 114 + 69
100
10 + 60 = 70
4 + 9 = 13
100 + 70 + 13 = 183
Terms
o Compensation model -> rounding, then subtracting at end
o Chunking -> "friendly numbers" like 10 or 5
o Partial sums -> piece at a time -> adding many times
o Decomposition
These are all chunking in different ways
*all these methods incorporate place value
Subtracting
o 1000 - 998