2.3 subtracting whole #s and decimals.notebook
September 30, 2011
Everyday Math
2.3
Unit 2 Lesson 3
Mental Math and Reflexes
Subtraction of Whole
Numbers and Decimals
Write these numbers in expanded notation
on your slates.
0.12
Objective: To review the
trade-first and partial-differences
methods for subtraction.
Reminder
Expanded notation
expresses a number
as the sum of the
values of each digit.
0.59
0.47
TLG Page 81
Getting Started
Unit 2 Lesson 3
Mental Math and Reflexes
2.3
Everyday Math
2.3
Everyday Math
1
7
Write these numbers in expanded notation
on your slates.
0.381
Solve each problem.
8.1 - 4.7 = ?
81 - 47 = ?
Reminder
Expanded notation
expresses a number
as the sum of the
values of each digit.
0.872
5
11
Math
Message
Mental Math and Reflexes
0.654
9
3
Describe how the two problems
are alike and different.
TLG Page 92
Getting Started
TLG Page 81
Getting Started
Mental Math and Reflexes
Math Message
1
7
9
Trade-First Method
3
5
11
Math
Message
2.3
Everyday Math
2.3
Everyday Math
Follow along with this example on page 15 in your SRB.
Follow Up
Subtract 275 from 463
100s
81 - 47 = 3.4
8.1 - 4.7 = 34
Why are these solutions incorrect?
100s
10s
1s
4
6
3
-2
7
5
100s
10s
4
5
6
1s
-2
7
5
10s
1s
3
4
15
5
6
13
3
-2
7
5
8
8
13
3
1
Look at the 1s place.
You cannot remove 5
ones from 3.
So trade 1 ten for 10
ones. Now look at the 10s
place.You cannot remove
7 tens from 5 tens.
So trade 1 hundred
for 10 tens. Now
subtract in each
column.
TLG P. 92
TLG P. 92
Part 1
Part 1
Math Message Follow up
Trade­First Method
1
2.3 subtracting whole #s and decimals.notebook
Everyday Math
September 30, 2011
Everyday Math
2.3
Partial-Difference Method
Follow along in your SRB on page 17.
The subtraction is performed left to right,
column by column.
4,261 - 2,637 = ?
4,261
- 2,637
Subtract the thousands: 4,000-2,000
Subtract the hundreds:
600-200
+ 2,000
- 400
(smaller number is on top, so include the minus sign)
Subtract the tens:
60-30
+
30
Subtract the ones:
7-1
-
6
(smaller number is on top, so include the minus sign)
Find the total: 2,000 - 400 + 30 - 6
2.3
Reviewing the
Partial-Difference Method
1,624
The smaller number in each column is always
subtracted from the larger number.
If the bottom number is less than the top number,
then the result will be added to obtain the final answer.
If the bottom number is greater than the top number ,
then the result will be subtracted to obtain the final
answer.
To find the final answer, the partial differences
are added or subtracted.
TLG p. 94
Part 1
Partial­Difference Method
TLG p. 94
Part 1
Reviewing Partial­Difference Method
2.3
Everyday Math
Math Journal
Open your journal to page 35
and complete the problems as
instructed in the directions.
Remember to use the workspace provided.
TLG P. 95
Part 1
Math Journal
Sep 18­8:25 PM
2.
2.3
Everyday Math
Subtraction Target Practice
Instructions are on page 331 in your SRB
or plan the decimal version.
Start with 20.
When 2 cards are turned over, use them to form a
decimal number that has one digit in the ones place and
one in the tenths place. (Use a counter for a decimal
point)
These numbers become the minuends. The game
continues until one player reaches 0 without going
below 0.
TLG P. 95
Part 2
Sep 18­8:30 PM
Subtraction Target Practice
2