7th Grade Math

470 Probability and Predictions

= Step-by-Step Solutions begin on page R1.

Extra Practice begins on page EP2.

3. RECREATION In a survey, 250 people from a
   town were asked if they thought the town
   needed a recreation center. The results are
   shown in the table.
   a. Predict how many of the 3,225 people in the
   town think a recreation center is needed.
   b. About how many of the 3,225 people would be undecided?


4. VOLUNTEERING A survey showed that 90% of teens donate money to a
   charity during the holidays. Based on that survey, how many teens in
   a class of 400 will donate money the next holiday season?

B Match each situation with the appropriate equation or proportion.

55 27 MP3s is what percent of 238 MP3s? a. n = 27 · 2.38

b. _ 10027 =

p

_ 238

c. 23827 = 100 n

6. 238% of 27 is what number?


7. 27% of MP3 owners download music weekly.
   Predict how many MP3 owners out of
   238 owners download music weekly.


8. CATS Use the graph that

43%

29%

17%

Training Cats

Problem

01020

Percent

30 40 50

Climbing on

Furniture

Clawing

Furniture

Fighting

with Other

Animals

shows the percent of cat

owners who train their

cats in each category.

a. Out of 255 cat owners,

predict how many

owners trained their

cat not to climb on

furniture.

b. Out of 316 cat owners,

predict how many more

cat owners have trained their cat not to claw on furniture than have

trained their cat not to fight with other animals.

9. MATH IN THE MEDIA Find real-world data using a newspaper or
   magazine, the television, or the Internet. Then write a question based on
   your data and survey a small group. Use your survey results to make a
   prediction.

C 10. CHALLENGE A survey found that 80% of teens enjoy going to the movies

in their free time. Out of 5,200 teens, predict how many said that they

do not enjoy going to the movies in their free time.

11. E WRITE MATH Explain how to use a sample to predict what a group
    of people prefer. Then give an example of a situation in which it makes
    sense to use a sample.

Recreation Center Needed

Response Percent

Yes 44%

No 38%

Undecided 18%

Examples 1 and 2

466_476_C08_L3_895130.indd 470 12/29/09 1:32 PM