Transcript Do Now 11/16/11

Do Now 12/2/13
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Copy HW in your planner.
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Text p. 116, #1-19 odds
Benchmark Test Chapters 1,2,3, & 11 Wednesday and
Thursday.
Objective
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SWBAT review adding, subtracting,
multiplying, and dividing decimals
ADDITION &
SUBTRACTION
REVIEW
Section 2.2 “Adding Integers”
Adding Two Integers with SAME signs
To add two integers with the SAME signs, add
the absolute values of the numbers. The answer
will have the same sign.
35 + 18
|35| = 35
|18| = 18
35 + 18 = 53
-35 + (-18)
|-35| = 35
|-18| = 18
35 + 18 = -53
Section 2.2 “Adding Integers”
Adding Two Integers with DIFFERENT signs
To add two integers with DIFFERENT signs,
subtract the smaller absolute value from the
greater absolute value and write the sign of the
integer with the greater absolute value.
-35 + 18
|-35| = 35
|18| = 18
Because 35 has a greater 35 – 18 = - 17
absolute value than 18 the
answer is “negative”.
Section 2.3
“Subtracting Integers”
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When subtracting two integers, ADD
the OPPOSITE of the second
number to the first.
8–5=
Instead of subtracting ADD
the OPPOSITE!!
Do the “OPP-OPP”
8“Opposite-Opposite”
+ (-5) = 3
ADD the OPPOSITE
Section 3-1
Adding & Subtracting Decimals
Add & subtract decimal numbers
by lining up the decimal point.
1.2 + 0.87
1.20
+0.87
2.07
Use a zero as
a placeholder
so that both
numbers are
in the same
place value
32.7 + (-62.82)
|32.7| = 32.7
|-62.82| = 62.82
62.82 – 32.7
Because 62.82 has a greater
absolute value than 32.7 the
answer is “negative”.
62.82
– 32.70
- 30.12
Use a zero as
a placeholder
so that both
numbers are
in the same
place value.
-5.23 – 9.1
Add the Opposite !!!
-5.23 + (-9.1)
To add two integers with the
SAME signs, find the sum of
their absolute values. Use the
sign of the two integers
5.23
+ 9.10
-14.33
Use a zero as
a placeholder
so that both
numbers are
in the same
place value.
“Real-Life”
During one month in the United States,
492.23 million commuter trips were taken
on buses, and 26.331 million commuter
trips were taken on light rail. How many
more trips were taken on buses than on
light rail?
492.230
– 26.331
465.899
million more trips were
taken on buses than on
MULTIPLICATION
REVIEW
“Multiplying Integers”
Rule #1
The product of two integers with the
same sign is always POSITIVE!
8 x 3 = 24
-8 · (-7) = 56
Rule #2
The product of two integers with
different signs is always NEGATIVE!
-6 x 3 = -18
8(-4) = -32
Section 3-2
Multiplying Decimals
To multiply decimals, multiply as you
would integers. To place the decimal point
in the product count the number of decimal
places in each factor. The product will
have the same number of decimal places
as the sum of the decimal places in the
factors.
Find the product.
-2.78
x 0.8
-2.224
-2224
-2.78 · 0.8
2 decimal places
1 decimal place
How many
decimal places
are in
each number?
How many
decimal places
are in the sum of
both numbers?
3 decimal places will then be in the product!
Find the product.
0.014
x -16
0084
+0140
-0.224
-0224
-16 x 0.014
3 decimal places
0 decimal places
How many
decimal places
are in
each number?
How many
decimal places
are in the sum of
both numbers?
3 decimal places will then be in the product!
“Real-Life”
The average snowfall in Howell, NJ is
18.55 inches per winter. What is the total
amount of snowfall in inches expected over
the next 2.5 years?
18.55
x 2.5
9275
37100
46.375
Inches of snowfall expected in the
next 2.5 years
DIVISION
REVIEW
Section 3-3 “Dividing Decimals”
How do you divide two decimal numbers
0.6 ÷ 0.3
or
0.3 0.6
divisor
By multiplying both numbers by the same power
of ten, you can make the divisor an integer.
Dividing by an integer is much easier than
dividing by a decimal.
0.3 0.6
Multiply both
numbers by 10
2
3 6
Find the quotient of -0.875 ÷ (-0.25)
0.25 0.875
Multiply both numbers
by 100 to make the
divisor an integer
35
25 87.5
75
12
125
Finished
25 87.5
Move the decimal point
straight up, then divide as
you normally would.
The quotient of two
integers with the same
sign is always
POSITIVE!
“Real-Life”
If Sandy and her family used 14.95
gallons of gas to drive 358.8 miles, how
many miles per gallon did the car get?
14.95 358.8
24
1495 35880
The car got 24 miles per gallon
24
Homework
Text p. 116, #1-19 odd
Joey is in the process of buying a new vehicle. He
has narrowed his options down to 2 choices. Which
vehicle gets better gas mileage (mpg)
and by how much?
2.5 gallons of gas
can go 48.5 miles
19.4
2.5 48.5
miles per gallon
24.25
– 19.4 0
4.85
6.8 gallons of gas
can go 164.9 miles
24.25
6.8 164.9
miles per gallon
The car gets 4.85
more miles per gallon
of gasoline than the
SUV.