READING DOT PLOTS AND FREQUENCY TABLES

Problem 1 :

Grade 3 students estimated how much television they watch each week, to the nearest hour. The dot plot shows the data.

How many students watched TV more than 9 hours and less than 14 hours ?

a)  9     b)  10     c)  11    d)  13

Solution :

More than 9 hours and less than 14 hours means, the number of students who are watching TV at 10, 11, 12, 13 hours.

=  7 + 6

= 13 hours

So, option d is correct.

Problem 2 :

A teacher asked 20 students how many books they read last summer. The dot plot displays the data. 

a) What is the greatest number of books a student read ?

b) How many students read 0 books?

Solution :

a) How we are understanding the dot plot ?

• 4 students read 0 books (no books)
• 6 students read 1 book.
• 4 students read 2 books.
• 1 student read 3 books.
• 2 students read 5 books
• 1 student read 8 books
• 1 student read 9 books
• 1 student read 10 books.

10 books read by 1 student is the greater.

b) 4 students read 0 books.

Problem 3 :

A scientist measured the temperature at which water boils. The table shows the results for 10 measurements.

Boiling point of water 

211.5     211.6     211.7    211.5    211.8

211.8      211.7     211.8    211.7    211.9

Which data plot represent the data ?

Solution :

From the given data, let us create frequency table.

211.5     211.6     211.7    211.5    211.8

211.8      211.7     211.8    211.7    211.9

This frequency table is represented in option d. So, option d is correct.

Problem 4 :

Researcher recorded the number of times lab rats completed a maize in 30 minutes. The table shows the data for 12 rats.

Maze Completions

15    12   15   12

13    11   10    13

11    14    12   13

Which dot plot represent the data ?

Solution :

Maze Completions

15    12   15   12

13    11   10    13

11    14    12   13

It is represented in option b. So, option b is correct.

Problem 5 :

A doctor asked 15 people how many hours they spend exercising each week. The dot plot displays the data.

What  do any cluster and gaps in the dot plot, tell you about the exercise habits of these people ?

Solution :

Most of the people, they do exercise 4 hours in a week.

Problem 6 :

The 25 students in a math class took turns flipping a coin 20 times each. the teacher recorded the number of times the result was heads. The dot plot displays the data.

How many students got 9 or 10 heads in 20 flips ?

Solution :

• 9 heads got by 5 students
• 10 heads got by 5 students

10 students got 9 heads or 10 heads