- Since many decimal numbers can be written as using fractions, we add them and subtract them in a manner similar to adding and subtracting fractions: add/subtract "like" fractions (same denominators and same decimal places)
Example:
24.076
+ 3.19
=27.266
Subtraction with decimal squares, one square is the unit.
Pencil and paper algorithm is the traditional way of doing addition and subtraction
2.4 5.6
+3.2 -3.4
=5.6 =2.2
Multiplication
Whole number x decimal
3 x 0.2
= 0.2 + 0.2 + 0.2
= 0.6
Area Model:
Pencil and paper algorithm:
Powers of 10:
Example:
0.3 (or 3/10) x 10^2 = 30
Example:
4.012 x 10^7
[4(1)+0(10^-1)+1(10^-2)+2(10^-3)] 10^7
Example:
28.7 x 10^-3
287/100 x 1/1000 = 287/10000 = 0.0287
Division:
Measurement/Subtractive
.9 / .3 = 3
---I---I---
Sharing/Partitive
.9 / 3= 3
(---) (---) (---)
This shows that 3 friends are each given 3 peices of candy
Paper and pencil algorithm:
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