Addition and Subtraction-
Many decimals numbers are written using fractions you can add and subtract them in a way similar to adding and subtracting fractions: you add and subtract "similar" fractions that have the same denominators and decimals that have the same decimal places.
Examples:
2.365 21.05 15.02 20.09
+7.257 +31.04 - 10.01 - 10.02
---------------- --------------- ----------- -------------
9.226 52.09 5.01 10.07
Mulitplication-
Think of multiplication as repeated addition.
Examples:
4*.06 So you have 4 groups of .06 added together .06+.06+.06+.06=.24
3*.2 So you have 3 groups of .2 added together .2+.2+.2=.6
You can also set multiplication up vertically:
Examples:
12.3
* 1.7 within the 2 numbers that you are mulitplying you have 2 decimal places so that is how many the answer will have
---------
861
+1230
------------
20.91 which has the 2 decimal places from above.
Division-
Sharing-
Think of handing out the peices that you have using the divisor as the number of people to hand out to and the dividend as the amout of objects you have to hand out.
Examples:0.10/2 so think of the problem as having 2 friends and having 10 books to hand out to them. ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ so if you hand the books out evenly to each friend they both get 5 but since you have a decimal you add the decimal back into the answer equalling .5
http://www.coolmath.com/prealgebra/02-decimals/06-decimals-adding-01.htm
This is a helpful website that give good and creative ideas of how to teach children the fundamentals of decimals.
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