Question

The line plot shows the number of phone calls made in one day by students in​ Dorothy’s class.
Number of Phone Calls
3
4
5
6
7
8
9
10
11
12
13
14
15



A dot plot labeled Results of Coin Tosses has a horizontal axis labeled Number of ~sideC from 5 to 15 in increments of 1. The graph consists of a series of plotted points from left to right. The number of dots on each horizontal axis label are as follows, where the label is listed first and the number of dots is listed second: 5, 1; 6, 1; 7, 2; 8, 2; 9, 4; 10, 4; 11, 5; 12, 3; 13, 2; 14, 0; 15, 1.
Question content area bottom
Part 1
Based on the information in the line​ plot, what is the probability a student
chosen at random made 12 or 13 phone calls that​ day?
A.three fifths
three fifths
B.seven ninths
seven ninths
C.four elevenths
four elevenths
D.one fifth
one fifth

Answer 1

To determine the probability that a randomly chosen student made either 12 or 13 phone calls, we need to follow these steps:

1. **Identify the number of students** who made 12 and 13 phone calls from the dot plot provided.
- Number of students who made 12 phone calls: 3 (as indicated by 12, 3)
- Number of students who made 13 phone calls: 2 (as indicated by 13, 2)

2. **Calculate the total number of students** represented in the dot plot. We can do this by summing the number of students for each count:
- 5 calls: 1
- 6 calls: 1
- 7 calls: 2
- 8 calls: 2
- 9 calls: 4
- 10 calls: 4
- 11 calls: 5
- 12 calls: 3
- 13 calls: 2
- 14 calls: 0
- 15 calls: 1

Total = 1 + 1 + 2 + 2 + 4 + 4 + 5 + 3 + 2 + 0 + 1 = 25 students

3. **Calculate the favorable outcomes** (students who made 12 or 13 phone calls):
- Total for 12 and 13 = 3 (for 12) + 2 (for 13) = 5

4. **Calculate the probability**:
\[
P(12 \text{ or } 13) = \frac{\text{Number of students who made 12 or 13 phone calls}}{\text{Total number of students}} = \frac{5}{25} = \frac{1}{5}
\]

Thus, the probability that a randomly chosen student made 12 or 13 phone calls that day is **D. one fifth**.