Transcript document

PSSA Math Review
Lesson 33 Making Predictions
Standards

E.4.1.2
Make predictions based on survey
results or graphs (bar, line, circle,
scatter plots, etc.)
Example 1

Last year, a store manager found
that 3 of every 10 T-shirts she sold
were black. If she expects to sell 500
T-shirts this year, how many can she
predict will be black?
Example 1 - Strategy

Use a proportion to predict the
result.
• Step 1: Set up a proportion.
Let t – the predicted number of black Tshirts.
 3/10 = t/500

• Step 2: Solve for t.
3/10 = t/500
 3 x 500 = 10 x t
 1,500/ 10 = t

Example 1 - Answer
150 = t
 The store manager can predict that
she will sell 150 black T-shirts.

Example 3
Rodney surveys students at Lincoln Middle
School to determine if they support going
to school in the summer. This circle graph
shows the results.
Do You Support Going to School in Summer?
50%
No
40%
Yes
10% Not
Sure
Example 3 – Cont.
There are 750 students at Lincoln
Middle School. How many are likely
to support going to school in the
summer?
50 %
No
40%
Yes
10%
Not
Sure
Example 2 - Strategy

Use the graph to make a prediction.
• Step 1: Identify the percent that voted
“Yes”. The graph shows that 40% of the
students voted “yes”.
• Step 2: Find 40% of the total number of
students. There are 750 students. Find
40% of 750.
40% x 750 = 0.4 x 750 = 300
Example 2 – Solution

Rodney can expect 300 students to
support going to school in the
summer.
Example 3
For a science experiment, Deanna
counts the number of fruit flies living in
a container each day. This graph shows
the results.
Population
Fruit Fly Population
40
35
30
25
20
15
10
5
0
1
2
3
4
5
Day
6
7
8
9
Example 3 – Cont.
How many fruit flies can she expect on the
10th day?
Fruit Fly Population
Population

40
35
30
25
20
15
10
5
0
1
2
3
4
5
Day
6
7
8
9
Example 3 - Strategy

Use the graph to make a prediction.
• Step 1: Identify the pattern of the
graph.
The line is increasing from left to right.
The rate of increase is slowing down as the
line ”rolls over”.
• Step 2: Extend the line.
• Step 3: Use the extended line to predict
the number for the tenth day.
The number for the tenth day is about 40.
Example 3 - Solution

Deanna should predict a population
of 40 fruit flies on the tenth day.
Sample Test Question
Question 1
There are 425 people living in Willie’s
apartment building. He asks 30 people about
their preferences in the election for building
president. Eighteen say they will vote for Mrs.
Adams. If everyone votes, how many votes can
Mrs. Adams expect in the election?
A.
B.
C.
D.
255
295
345
395
Question 1 - Solution

Set up a proportion:
18/30 = x/425
18 x 425 = 30x
7650/30 = x
255 = x
Mrs. Adams can expect to receive
255 votes in the election.
Question 2
Cell Phone Ownership
Number of Cell Phones
This bar graph shows
the number of cell
phones owed by
students in each
grade at Booker T.
Washington School.
What is the best
prediction for the
number of cell
phones owned by 9th
graders?
300
250
200
8th
150
6th
7th
100
50
5th
0
Grade
Question 2 – Cont.
A.
B.
C.
D.
What is the best prediction for the
number of cell phones owned by 9th
graders?
Cell Phone Ownership
240
300
250
250
200
270
8th
150
6th
7th
300
Number of Cell Phones

100
50
5th
0
Grade
Question 2 - Solution

The best prediction is C. 270.
Question 3
Which term best describes the
correlation between cost and the number
of radios sold?
Radio Sales
B.
C.
D.
Strong positive
Strong negative
Weak negative
No correlation
Numbers Sold
A.
30
25
20
15
10
5
0
0
10
20
30
40
Radio Prices (in dollars)
50
60
Question 3 – Solution

Strong negative correlation.
Question 4
How many radios are likely to be sold if
the price is set at $34?
B.
C.
D.
24
28
32
38
35
Numbers Sold
A.
Radio Sales
30
25
20
15
10
5
0
0
10
20
30
40
Radio Prices (in dollars)
50
60
Question 4 - Solution
32 radios will likely be sold.
 C.

Question 5
T.J. surveyed 60 students in his
school about their after-school
activities. The results are shown in
this graph.
50%
Sports
25% Clubs
15%
Band
10%
Yearbook
Question 5 – Cont.
If there are 800 students in the
school, how many can T.J. expect to
be in the band?
A.
B.
C.
D.
9
60
80
120
50%
Sports
25%
Clubs
15%
Band
10%
Yearbook
Question 5 - Solution
First find 15% of 60.
.15 x 60 = 9
9 students out of 60 are in the band.
Next, set up a proportion.
9/60 = x/800
Cross multiply:
9 x 800 = 60x
Solve for x:
7200/60 = x
120 = x
Question 6
A.
B.
C.
D.
170
190
210
230
miles
miles
miles
miles
per
per
per
per
hour
hour
hour
hour
Speed (mi/hr)
This graph shows the speed of a race car
during its first few seconds off the
starting line. If the pattern continues,
how fast can you expect the car to go in
the tenth second?
Racecar Speeds
200
180
160
140
120
100
80
60
40
20
0
1
2
3
4
5
6
Time (sec)
7
8
9
Question 6 - Solution

B. 190 mph
Open Ended Question
Felicia buys a box of 200 filled chocolates.
She eats 8 of them and finds that 3 are
caramel-filled.
A.
B.
How many chocolates in the box can she
expect to be caramel-filled?
Use what you know about making
predictions to explain why your answer is
correct. Use words and/or numbers in
your explanation.
Open Ended


A. She can expect 75 of the chocolates to be
caramel-filled.
B. First you set up a proportion to help estimate
the total amount that could possibly be caramelfilled.
3/8 = x/200
Next you cross multiply to solve for x.
3 x 200 = 8x
Then you divide both sides by 8 to get x by itself.
600/8 = x
Finally you solve for x and this will tell you an
approximate prediction for the number of
chocolates that will be caramel-filled.
75 = x