Decimals Operations Addition (lesson 1) - Revision history

Kdmullins: /* Variation */

2020-08-20T17:29:06Z

‎Variation

Kdmullins: /* Presentation */

2020-08-20T17:27:57Z

‎Presentation

Kdmullins: A concrete experience of adding decimals, stressing the importance of lining up the decimal points.

2020-08-20T15:14:39Z

A concrete experience of adding decimals, stressing the importance of lining up the decimal points.

New page

=== Age ===

9-12 

=== Materials ===

* Decimal board
* Decimal beads and disks
* Three sets of decimal numeral cards
* Cardboard strip as long as the decimal board
* Prepared problems
* Paper and pencil

* Optional/Alternative: Montessori bead bars

 

=== Preparation ===

Students should have had the Introductory Decimal Lessons 1-9.

 

=== Presentation ===

*Teacher can choose to use bead bars for this lesson to help make an impression for the difference in values.
* 1. Select the first problem: 8.38 + 6.75
* 2. Make the top addend with cards, and place it to the left of the board. Then make the second addend with cards, placing it under the first. Place the cardboard strip under both.
* 3. Form the first addend with beads and disks on the board. Then form the second addend on the board, leaving a space between the two addends.

Picture 1 from page 59

* 4. Begin adding with hundredths: 8 + 5 = 13. Exchange the hundredths for a tenth, leaving three thousandths. continue adding tenths, then units- exchanging when necessary, until the sum is reached. When the addition is complete, get the small cards corresponding to the sum, and place them under the addend cards.

Picture 2 on page 59

NOTE:
* Provide examples that offer many opportunities for exchanging, e.g., 0.999999 + 0.000001
* Provide other problems with addends having unequal numbers of decimal places, '''''Italic text'''Pointing out the importance of lining up the decimal mounts inside the proper place values.'' Example: 32.285 + 7.94
* Provide other problems with more than two addends or with addends written horizontally, e.g. 52.74 + 6.5 + 23.88 =

* Most students will work with this material for a very short time, because they will be able to internalize the procedure and proceed abstractly.

=== Control Of Error ===

Teacher guided; lining up the disks in the proper decimal place values. 

=== Points Of Interest ===

Participating with the new knowledge helps move the concrete experiences toward abstract thinking 

=== Purpose ===

*To make a visual, auditory and kinesthetic impression upon the student on how to perform operations with decimals.

 

=== Variation ===

Alternative: Use bead bars instead of beads and disks:
Picture 3

 

=== Handouts/Attachment ===

 

[[Category:Mathematics]] [[Category:Mathematics_9-12]]

@@ Line 59: / Line 59: @@
 === Variation  ===
-Alternative: Use bead bars instead of beads and disks:
+Alternative: Use bead bars instead of beads and disks.
-Picture 3
 <br>

@@ Line 30: / Line 30: @@
 * 3. Form the first addend with beads and disks on the board. Then form the second addend on the board, leaving a space between the two addends.
-Picture 1 from page 59
+[[File:Adding_with_decimals_1_page_59.jpg|300px]]
 * 4. Begin adding with hundredths: 8 + 5 = 13. Exchange the hundredths for a tenth, leaving three thousandths. continue adding tenths, then units- exchanging when necessary, until the sum is reached. When the addition is complete, get the small cards corresponding to the sum, and place them under the addend cards.
-Picture 2 on page 59
+[[File:Adding_with_decimals_2_page_59.jpg|300px]]
 NOTE: