Question

a study of 900 working women showed that their feelings changed throughout the day. the line graph shows 15 different times in a day and the average level of happiness for the women at each time. based on the information given by the graph, represent the set using the roster method. {x | x is a time of the day when 3 < average level of happiness < 4} choose the correct answer below. a. {20, 21} b. {12, 20} c. {12, 20, 21} d. {20}

Explanation:

Step1: Identify target happiness range

We need times where $3 < \text{happiness} < 4$.

Step2: Match times to happiness values

Check the graph:

• Time 12: Happiness = 3.5 (fits $3<3.5<4$)
• Time 20: Happiness = 3.5 (fits $3<3.5<4$)
• Time 21: Happiness = 3.5 (fits $3<3.5<4$)

Step3: Compile roster set

Collect all valid times into a set.

Answer:

C. {12, 20, 21}