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Grade 6 ,QYHVWLJDWHFKDQFHSURFHVVHVDQGGHYHORSXVHDQGHYDOXDWH
SUREDELOLW\PRGHOV
SDAP 3.3 Represent probabilities as ratios, proportions, decimals
between
0 and 1, and percentages between 0 and 100 and
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verify that the probabilities computed are reasonable; know that
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if P is the probability of an event, 1-P is the probability of an
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DURXQGLQGLFDWHVDQHYHQWWKDWLVQHLWKHUXQOLNHO\QRUOLNHO\DQGDSUREDELOLW\QHDU
event not occurring.
UNDERLYING SKILLS AND CONCEPTS:
predict events
Represent Probability As a Ratio
The probability of an event can be expressed as a ratio that compares
the number of ways an event can occur to the number of possible
outcomes. When each outcome is as likely as any other outcome, the
probability is:
number of ways an event can occur
Probability ! """"""""
number of possible outcomes
Probability can be expressed in words or as a fraction.
If an event is certain, it has a probability of 1.
If an event is impossible, it has a probability of 0.
E x am p l E
1
If you took a marble without looking, what is the probability
that you will pick a striped marble?
2
The probability is 2 possibilities out of 7, or "7 .
Trick question: What is the probability that you will pick
a cube? ZERO! There are no cubes in the bag.
E x am p l E
2
Marius has 3 long pencils and 9 short pencils in a pack.
If he picks one pencil without looking, what is the probability
that he will pick a long pencil?
Remember to first find out
how many there are in all!
3 # 9 ! 12 in all.
There are 12 pencils in all. 3 out of 12 are long.
1
3
number of long pencils
P = """"
! ", or "
total number of pencils
12
4
Trick question: What is the probability that you will pick
a pencil. ONE! There are only pencils in the pack, so you are
certain to pick a pencil.
page 376
Chapter 32 – Lesson 2
E – © CSL Associates, Inc. All rights reserved.
number of striped marbles
2
"""" ! "
number of marbles
7
Name
P RAC T I C E
Give the probability for each situation.
1. There are 15 red cubes and 2 blue cubes
2. There are 15 red cubes and 10 blue
in a bag. Picking a red cube?
cubes in a bag. Picking a red cube?
15
17
15
3
or 25
5
3. There are 5 red cubes, 7 blue cubes, and
3 green cubes. Picking a red cube?
5
1
or 15
3
4. There are 6 white socks, 8 pink socks,
and 4 black socks in a drawer. Picking a
black sock?
4
2
or 18
9
Write the probability for each outcome.
5. Landing on an even number?
5
8
1
E – © CSL Associates, Inc. All rights reserved.
6. Landing on an odd number?
3
8
2
8
3
7
4
7. Landing on a number less than 9?
8
, or 1
8
8. Landing on a number greater than 8?
6
0
, or 0
8
Math
Reasoning
4
Predict
MR 2.3, 3.1
9. A box has 20 crayons. 10 are blue and 10 are yellow.
Which is more likely, picking a blue crayon or picking a yellow one?
Explain your answer.
The outcomes are equally likely to happen because there
are the same number of blue and yellow.
Chapter 32 – Lesson 2
page 377
MCX94.HW.CL.G5.FM&Lesson.v211
8/2/04
18:03
Page 252
Name
…at home!
P RAC T I C E
Give the probability for each situation.
1. There are 12 red cubes and 4 blue cubes
2. There are 12 red cubes and 10 blue
in a bag. Picking a red cube?
cubes in a bag. Picking a red cube?
12
3
or 16
4
12
6
or 22
11
3. There are 6 red cubes, 9 blue cubes, and
2 green cubes. Picking a red cube?
6
17
4. There are 8 white socks, 6 pink socks,
and 2 black socks in a drawer. Picking
a black sock?
2
1
or 16
8
Write the probability for each outcome.
5. Landing on an even number?
1
6. Landing on an odd number?
3
8
2
8
3
7
4
7. Landing on a number less than 9?
8
, or 1
8
8. Landing on a number greater than 8?
6
0
, or 0
8
Math
Reasoning
6
Predict
MR 2.3, 3.1
9. A bundle has 18 balloons. 9 are red and 9 are purple.
Which is more likely, picking a red balloon or picking a purple one?
Explain your answer.
The outcomes are equally likely to happen because there are
the same number of red and purple balloons.
page 252
Home Resource and Homework
Chapter 32 Lesson 2
E – © CSL Associates, Inc. All rights reserved.
5
8
MCX94TEG5CH01_32.v7.4.2 2/24/01 19:51 Page 693
Name
P RAC T I C E
Give the probability for each situation.
1. There are 15 red cubes and 2 blue cubes
2. There are 15 red cubes and 10 blue
in a bag. Picking a red cube?
cubes in a bag. Picking a red cube?
15
17
15
3
or 25
5
3. There are 5 red cubes, 7 blue cubes, and
3 green cubes. Picking a red cube?
5
1
or 15
3
4. There are 6 white socks, 8 pink socks,
and 4 black socks in a drawer. Picking a
black sock?
4
2
or 18
9
Write the probability for each outcome.
5. Landing on an even number?
5
8
1
E – © CSL Associates, Inc. All rights reserved.
6. Landing on an odd number?
3
8
2
8
3
7
4
7. Landing on a number less than 9?
8
, or 1
8
8. Landing on a number greater than 8?
6
0
, or 0
8
Math
Reasoning
4
Predict
MR 2.3, 3.1
9. A box has 20 crayons. 10 are blue and 10 are yellow.
Which is more likely, picking a blue crayon or picking a yellow one?
Explain your answer.
The outcomes are equally likely to happen because there
are the same number of blue and yellow.
Chapter 32 – Lesson 2
Student Book Page
page 377
Name
…at home!
P RAC T I C E
Give the probability for each situation.
1. There are 12 red cubes and 4 blue cubes
2. There are 12 red cubes and 10 blue
in a bag. Picking a red cube?
cubes in a bag. Picking a red cube?
12
3
or 16
4
12
6
or 22
11
3. There are 6 red cubes, 9 blue cubes, and
2 green cubes. Picking a red cube?
6
17
4. There are 8 white socks, 6 pink socks,
and 2 black socks in a drawer. Picking
a black sock?
2
1
or 16
8
Write the probability for each outcome.
5. Landing on an even number?
1
6. Landing on an odd number?
3
8
2
8
3
7
4
7. Landing on a number less than 9?
8
, or 1
8
8. Landing on a number greater than 8?
6
0
, or 0
8
Math
Reasoning
6
Predict
MR 2.3, 3.1
9. A bundle has 18 balloons. 9 are red and 9 are purple.
Which is more likely, picking a red balloon or picking a purple one?
Explain your answer.
The outcomes are equally likely to happen because there are
the same number of red and purple balloons.
page 252
Home Resource and Homework
Chapter 32 Lesson 2
E – © CSL Associates, Inc. All rights reserved.
5
8