Predicting with Probability

A principal randomly chose 40 students from grade 5. Of these students, 9 were wearing watches. Based on this information, what is the most reasonable prediction of the number of students wearing watches in a group of 120 students from grade 5?

• 27
• 9
• 18
• 80

100 second graders were asked to do a book report about one of these four zoo animals.  The number of students who chose each animal is shown in the table.  If 250 second graders had to choose of of the four animals, predict how many would choose to write about a giraffe.

• 60 students
• 50 students
• 40 students
• 30 students

Aaron took a multiple choice test.  There were 25 questions, of which he answered 4 incorrectly.  At this rate, how many questions should Aaron expect to answer incorrectly if he takes a test with a total of 150 questions?

• 123
• 24
• 373
• 47

The probability of a video game being defective is 1 out of 20.  About how many video games would be defective in a shipment of 490 video games? (Round your answer to the nearest whole number.)

• 490
• 25
• 98
• 100

There are 480 students in Marla’s school.  In her classroom, there are 3 left-handed students and 17 right-handed students.  Predict the number of left-handed students in the whole school.

• 72
• 85
• 124
• 208

An ice-skating rink inspects 25 pairs of skates and finds 2 pairs to be defective.  The rink has 175 pairs of ice skates. Predict the number of pairs that are likely to be defective.

• 14
• 50
• 7
• 65

Shannon made the last 12 out of 20 shots for the varsity basketball team.  How many shots would you expect him to make in his next 160 shot attempts?

• 96
• 120
• 24
• 80

The results of a random survey showed that 42 out of 84 people plan to vote for Coach Vasquez for teacher of the month. Which is the best prediction of the total number of votes he will receive if 2,000 people vote?

• 825
• 750
• 1200
• 1000

In this jar of 20 jellybeans, 8 are pink. How many would be pink in a jar of 100?

• 20

• 40

• 5

• 100

The probability of a table-tennis ball being defective is 1 out of 10 . About how many balls would be defective in a case of 725 table-tennis balls? (Round your answer to the nearest whole number.)

• 73
• 125
• 80
• 310