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Wednesday, October 26, 2011

Derec's Math Post

Adding and Subtracting Decimal

To add decimal numbers:

1. Put the numbers in a vertical column, aligning the decimal point.
2. Add each column of digits, starting on the right and working and working left . If the sum of a column is more than ten, "carry" digits to the next column on the left.
3. Place the decimal point in the answer directly below the decimal points in the terms.n

(+) + (+) = +
(-) + (+) = -
(+) + (-) = Absolute Value
(-) + (+) = which ever is greater, keep the sign

Subtracting Decimal .
1. Put the numbers in a vertical column, aligning the decimal points.
2. Subtract each column, starting on the right and working left. If the digit being subtracted in a column is larger than the digit above it, "borrow" a digit from the next column to the left.
3. Place the decimal point in the answer directly below the decimal points in the terms.
4. Check your answer by adding the result to the number subtracted. The sum should equal the first number.

(+) - (-) = +
(-) - (+) = -
(+) -(+) = Absolute Value
(-) - (-) = Absolute value

For example.

89.9 + 43.3 = 133.2
1 1
+ 43.3
133 .2

46.65 - 16.2 = 30.45

- 16.20

Multiplying and Dividing Decimal

Here are the rules for multiplying decimal numbers:

1. Multiply the numbers just as if they were whole numbers:
*Line up the numbers on the right--do not align the decimal points.
*Starting on the right, multiply each digit in the top number by each digit in the bottom number, just as with whole numbers.
*Add the products.
2.Place the decimal point in the answer by starting at the right and moving the point the number of places equal to the sum of the decimal places in both numbers multiplied.

(-) x (+) = -
(+) x (-) = -
(+) x (+) = +
(-) x (-) = +

for example

37.7 x 2.8 =

37.7 ( 1 decimal place )
x 2.8 ( 1 decimal place )
+ 754
105.56 ( 2 decimal places, move point 2 places left )

To divide decimal numbers:

1. If the divisor is not a whole number, move decimal point to right to make it a whole number and move decimal point in dividend the same number of places.
2. Divide as usual. Keep dividing until the answer terminates or repeats.
3. Put decimal point directly above decimal point in the dividend.
4. Check your answer. Multiply quotient by divisor.

-/- = +
+/+ = +
-/+ = -
+/- = -

for example:

16.9 ÷ 6.5 = 2.6

6.5 /169.0
- 130
- 390

To check our answer, we multiply the quotient by the divisor and make sure it equals the dividend:

x 6.5
+ 156

-Finish all worksheets
-Homework Book
-Math Textbook;leftover work


  1. Great Post Derec. Your post was really organized and the explanation is right before the examples. There are some spelling mistakes and also for the examples. I think a picture would've worked better. Also adding a link or video might help. Great Job.

  2. Nice post! Your post explained everything pretty well and you have all the steps down. Instead of tpying everything, put a picture beside the steps so it makes it more appealing to look at. It also makes everything more clear for your blog viewers. Try adding more colour into your blog so the important things can stand out. Other than that, good job!

  3. Great job Derec. Your post was well organized and explained everything very well. I would suggest that you add a picture under the explanation of how you did it, because it was rather confusing. I also suggest you highlight important parts of your blog with different colours, other than that great job.

  4. Great post derec! You explained everything we did in class well, good job including the step s but next you shoul make the steps more clear like draw an example. Good job reminding what was for hoework. Keep up the good work!

  5. Good job Derec! I liked how you explained everything well. You also had a lot of information. On the other hand, you should have added pictures, links, colors, or videos to this blog. Although, you did a great job!

  6. Great post Derec! You had a lot of information. You explained things really well. Next time add some colors and pictures to make your post stand out more. Also try adding a video or link next time. Other than that, great job.