Respuesta :
Using the mean concept, it is found that a range of scores between 17 and 53 will give Lisa a C for the semester.
What is the mean?
- The mean of a data-set is given by the sum of all observations in the data-set divided by the number of observations.
In this problem, we have that:
- The data-set is composed by her 4 grades, which are: 90, 82, 91 and x.
Hence, the mean is:
[tex]M = \frac{90 + 82 + 91 + x}{4} = \frac{263 + x}{4}[/tex]
For a grade between 70 and 79, we have that:
[tex]70 \leq M \leq 79[/tex]
Then:
[tex]M \geq 70[/tex]
[tex]\frac{263 + x}{4} \geq 70[/tex]
[tex]263 + x \geq 280[/tex]
[tex]x \geq 17[/tex]
[tex]M \leq 79[/tex]
[tex]\frac{263 + x}{4} \leq 79[/tex]
[tex]263 + x \leq 316[/tex]
[tex]x \leq 53[/tex]
A range of scores between 17 and 53 will give Lisa a C for the semester.
You can learn more about the mean concept at https://brainly.com/question/13451786
