do now 11/14/11 copy hw in your planner. copy hw in your planner. text p. 102, #10-40 evens, #42,...
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Do Now 11/14/11Do Now 11/14/11
Copy HW in your planner.Copy HW in your planner. Text p. 102, #10-40 evens, #42, 43, 48, Text p. 102, #10-40 evens, #42, 43, 48,
& 49& 49
In your journal, define the word In your journal, define the word “decimal.” Then describe as many “decimal.” Then describe as many situations in real-life as you can situations in real-life as you can where you might need to add or where you might need to add or subtract decimals.subtract decimals.
Section 3-1Section 3-1Adding & Subtracting Adding & Subtracting
DecimalsDecimalsAdd & subtract decimal numbers Add & subtract decimal numbers
by lining up the decimal point. by lining up the decimal point.
1.2 +0.87
2.07HUNDREDTH
s
TENTH
S
One
s
1.2 + 0.871.2 + 0.87
0 Use a zero as a placeholder so that both numbers are in the same place value
9 +3.245
12.245
HUNDREDTHs
TENTH
S
One
s
9 + 3.2459 + 3.245
. Use zeros as a placeholders so that both numbers are in the same place value.
000TH
OUSANDTH
s
Put the decimal point afterany whole numbers.
12.49– 7.2
5.29HUNDREDTH
s
TENTH
S
One
s
12.49 – 7.212.49 – 7.2
0Use a zero as a placeholder so that both numbers are in the same place value
Tens
14 – 7.32
6.68HUNDREDTH
s
TENTH
S
One
s
14 – 7.3214 – 7.32
.Use zeros as a placeholders so that both numbers are in the same place value.
00Te
ns
Put the decimal point afterany whole numbers.
|35| = 35|35| = 35
35 + 1835 + 18
Adding Two Integers with SAME signsAdding Two Integers with SAME signs
To add two integers with the SAME To add two integers with the SAME signs, find the sum of their absolute signs, find the sum of their absolute values. Use the sign of the two integers. values. Use the sign of the two integers.
|18| = 18|18| = 18
35 + 18 35 + 18 = 53 = 53
|-35| = 35|-35| = 35
-35 + (-18)-35 + (-18)
|-18| = 18|-18| = 18
35 + 18 35 + 18 = 53 = 53 - -
Remember this?““Adding Integers”Adding Integers”
|-35| = 35|-35| = 35
-35 + 18-35 + 18
Adding Two Integers with DIFFERENT Adding Two Integers with DIFFERENT signssigns
To add two integers with To add two integers with DIFFERENT signs, find the difference of DIFFERENT signs, find the difference of their absolute values. Use the sign of their absolute values. Use the sign of the integer with the greater absolute the integer with the greater absolute value. value.
|18| = 18|18| = 18
35 – 18 35 – 18 = 17 = 17 - - Because 35 has a greaterBecause 35 has a greaterabsolute value than 18 the absolute value than 18 the answer is “negative”.answer is “negative”.
Remember this?““Adding Integers”Adding Integers”
Negative or Positive?Negative or Positive? Without solving the problem, decide Without solving the problem, decide
whether the sum will be positive, whether the sum will be positive, negative, or zero.negative, or zero.
7.2 + (-4.36)7.2 + (-4.36)positivepositive
-13.3 + 11.76-13.3 + 11.76negativnegativ
ee
-3.3 + 3.3-3.3 + 3.3zerozero
-7.3 + (-6.72)-7.3 + (-6.72)negativenegative
““Subtracting Integers” Subtracting Integers” When subtracting two integers, When subtracting two integers,
ADD the OPPOSITEADD the OPPOSITE of the of the second number to the first. second number to the first.
-8 – 15 = -8 – 15 = Instead of subtracting ADD Instead of subtracting ADD the OPPOSITE!! the OPPOSITE!!
-8 -8 + (-15)+ (-15) = =ADD the OPPOSITE ADD the OPPOSITE
-23-23Do the “OPP-OPP”Do the “OPP-OPP”““Opposite-Opposite”Opposite-Opposite”
Remember this?
Negative or Positive?Negative or Positive? Without solving the problem, decide Without solving the problem, decide
whether the sum will be positive, whether the sum will be positive, negative, or zero. (HINT: write the negative, or zero. (HINT: write the problem as a sum).problem as a sum).
1.7 – (-2.2)1.7 – (-2.2)
positivepositive
-1.36 – 1.1-1.36 – 1.1
negativnegativee
-0.14 – (-0.14)-0.14 – (-0.14)
zerozero
7.3 – 8 7.3 – 8 negativenegative
1.7 + (+2.2)1.7 + (+2.2)
-1.36 + (-1.1)-1.36 + (-1.1)
-0.14 + (+0.14)-0.14 + (+0.14)
7.3 + (-8) 7.3 + (-8)
Add the Opposite !!!Add the Opposite !!!
62.82 – 32.7
30.12HUNDREDTH
s
TENTH
S
One
s
32.7 + (-62.82)32.7 + (-62.82)
Use a zero as a placeholder so that both numbers are in the same place value.
Tens
|32.7| = 32.7|32.7| = 32.7 |-62.82| = 62.82|-62.82| = 62.82
62.82 – 32.7 62.82 – 32.7
- - Because 62.82 has a greaterBecause 62.82 has a greaterabsolute value than 32.7 the absolute value than 32.7 the answer is “negative”.answer is “negative”.
0
5.23 + 9.1
14.33HUNDREDTH
s
TENTH
S
One
s
-5.23 – 9.1-5.23 – 9.1
Use a zero as a
placeholder so that
both numbers are in the
same place value.- -
0
-5.23 + (-9.1)-5.23 + (-9.1)Add the Opposite !!!Add the Opposite !!!
To add two integers To add two integers with the SAME signs, with the SAME signs, find the sum of their find the sum of their absolute values. Use absolute values. Use the sign of the two the sign of the two integersintegers
““Real-Life”Real-Life”During one month in the United During one month in the United
States, 492.23 million commuter States, 492.23 million commuter trips were taken on buses, and trips were taken on buses, and 26.331 million commuter trips were 26.331 million commuter trips were taken on light rail. How many more taken on light rail. How many more trips were taken on buses than on trips were taken on buses than on light rail? light rail? 492.23492.2300
– – 26.33126.331
465.899465.899million more trips million more trips were taken on buses were taken on buses than on light railthan on light rail
2424
HomeworkHomeworkText p. 102, #10-40 evens, #42, Text p. 102, #10-40 evens, #42,
43, 48, & 4943, 48, & 49