Mental Math Grade 6 Teacher's Guide

4.2 + 3.5 = 6.3 + 1.6 = 4.2 + 3.7 =
6.1 + 2.8 = 0.32 + 0.56 = 2.08 + 3.2 =
4.15 + 3.22 = 5.43 + 2.26 = 6.03 + 2.45 =
15.45 + 1.25 = 43.30 + 7.49 = 70.32 + 9.12 =
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• Finding Compatibles (Review)
This strategy for addition involves looking for pairs of numbers that
combine to make a sum that will be easy to work with. Some examples
of common compatible numbers include 1 and 9; 40 and 60; 75 and 25
and 300 and 700.
Examples
a) For 3 + 8 + 7 + 6 + 2, think,“3 + 7 is 10, 8 + 2 is 10, so 10 + 10 + 6 is 26.”
b) For 25 + 47 + 75, think, “25 and 75 is 100, so 100 and 47 is 147.”
c) For 400 + 720 + 600, think, “400 and 600 is 1000, so the sum is 1720.”
d) For 3000 + 7000 + 2400, think, “3000 and 7000 is 10 000, so 10 000
and 2400 is 12 400.”
Practice Items
11 + 59 = 60 + 30 + 40 =
75 + 95 + 25 = 475 + 25 =
625 + 75 = 300 + 437 + 700 =
800 + 740 + 200 = 900 + 100 + 485 =
400 + 1600 + 3000 = 9000 + 3300 + 1000=
3250 + 3000 + 1750 = 2200 + 2800 + 600 =
3000 + 300 + 700 + 2000 = 3400 + 5600 =
0.6 + 0.9 + 0.4 + 0.1 = 0.2 + 0.4 + 0.8 +=
0.7 + 0.1 + 0.9 + 0.3 = 0.25 + 0.50 + 0.75 =
0.4 + 0.5 + 0.6 + 0.2 + 0.5 = 0.45 + 0.63 = 0.80 + 0.26 =
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Mental Math – Grade 6 29