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Unit 3 Test Review – Signed Decimals
A. Rules
Signs for * & /
Negative and Negative = _________ Positive and Positive = ______________
Negative and Positive = __________ Positive and Negative = ______________
Multiplying
The amount of numbers behind the decimal in the problem _________________ the
Decimals
amount of numbers behind the decimal in the answer.
Dividing Decimals
The ______________ number goes in the house, and the ____________ number is left
out in the cold. Move the decimal so the _________________ number is a whole
number. Move the other decimal _____________________.
Signs for + and –
Adding:
3 words for
Subtraction:
_______________ signs, add and keep
_______________
_______________ signs, subtract
_______________
Take the sign of the _______________ number
_______________
Then you’ll be exact!
Adding/Subtracting
Always __________________________ the decimals
Decimals
True or False: Think of MONEY
B. Multiplying Decimals
Problem
Estimate FIRST
15.6  0.6
16  1  16
 34.54  4.8
 1.467  (3.4)
Work Space
EXACT Answer
9.36
1678  (0.45)
C. Adding and Subtracting Decimals
Problem
Estimate FIRST
15.6  (0.6)
16  1  17
 34.54  4.8
 1.467  (3.4)
1678  0.45
Work Space
EXACT Answer
16.2
-0.32 – 4 + 60.02
D. Dividing Decimals
Problem
Estimate FIRST
Work Space
27.27 ÷ 2.7
1.452 ÷(-0.6)
20.026 ÷ 3.4
E. Scientific Notation and Standard Form (Lesson 4.7)
Change from scientific notation
to standard form.
1.
3.081´10-5 =
EXACT Answer
2.
8.3847 ´102 =
4. 0.785 =
3.
3.6245 ´10-2 =
5. 5300 =
Change from standard form to
6. 54785 =
scientific notation.
F. Word Problems
1. It snowed 4.6 inches in December, 5.3 inches in January, 8.7 inches in February, and 2.1 inches in
March. What was the average snowfall for that winter?
2. The highest recorded temperature in the world was Azizia, Libya on September 13, 1922. The
temperature was 58 degrees Celsius. The lowest temperature, -88.3 degrees Celsius was recorded at
the Soviet Antarctic station Vostok on August 24, 1960. What is the difference in these two
temperatures?
3. The 1937 Detroit football team holds the National Football League record for few penalties in a
season. They received 19 penalties and lost an average of -7.3 yards per penalty. Write a decimal to
represent how many yards they lost in all as a result of the penalties?
G. Order from least to greatest. Use the original numbers in your answer.
a. -3.435; -3.245; -3.543; -3.34; -3.152; -3.24
b.
5.61´106; 0.0054; 5.1´103; 5.3 ´10-3; 5.8 ´100; 520
H. Challenge!
1.23 + ( 7.4 - ( -3.4 )) · 0.09 - 5.1
0.25
Study Guide Answer Key
A. RULES
Negative and Negative = POSITIVE
Positive and Positive = POSITIVE
Negative and Positive = NEGATIVE
Positive and Negative = NEGATIVE
The amount of numbers behind the decimal in the problem EQUALS/IS THE SAME AS the amount of
numbers behind the decimal in the answer.
The FIRST number goes in the house, and the SECOND number is left out in the cold. Move the
decimal so the OUTSIDE number is a whole number. Move the other decimal THE SAME NUMBER OF
SPACES.
Adding:
3 words for Subtraction:
SAME signs, add and keep
KEEP, CHANGE, CHANGE
DIFFERENT signs, subtract Take the sign of the HIGHER number ,
Always LINE UP the decimals
True or False: Think of MONEY
E. SCIENTIFIC NOTATION
B. MULTIPLYING DECIMALS
1.
0.00003081
-34 * 5 = -175, -34.54 * 4.8 = -165.792
2.
838.47
5.
5.3 x 103
-1 * -3 = 3, -1.467 * -3.4 = 4.9878
3.
0.03624
6.
5.4785 x
1678 * 0 = 0, 1678 * -0.45 = 755.1
4.
7.85 x 10-1
104
C. ADDING/SUBTRACTING
-35 – 5 = -40, -34.54 – 4.8 = -39.34
-1 + -3 = -4, -1.467 + -3.4 = - 4.867
1678 – 0 = 0, 1678 – 0.45 = 1677.55
0 – 4 + 60 = 56, -0.32 – 4 + 60.02 =
55.7
D. DIVIDING DECIMALS
27 / 2 = 13.5, 27.27 / 2.7 = 10.1
1 / -1 = =1, 1.452 / -0.6 = -2.42
20/4 = 5, 20.026/3.4 = 5.89
F. WORD PROBLEMS
1. 5.175 in
2. 146.3 degrees 3. -
138.7yds
G. ORDERING
1. -3.543; -3.435; -3.34; -3.245; -3.24; 3.152
2.
5.3 ´10-3; 0.0054; 5.8 ´100; 520;
5.1´103; 5.61´106
CHALLENGE -4.8