Question

In your​ class, you have scores of 66​, 74​, 71​, and 81 on the first four of five tests. To get a grade of Upper C​, the average of the first five tests scores must be greater than or equal to 70 and less than 80. a. Solve an inequality to find the least score you can get on the last test and still earn a Upper C. b. What score do you need if the fifth test counts as two​ tests?

Answer 1

Answer:

A score of greater than equal to 128 and less than 188 will get a grade of Upper C

Step-by-step explanation:

We are given the following in the question:

Scores:

66​, 74​, 71​, 81

Let x be the score on fifth test.

$\text{Average} = \displaystyle\frac{\text{Sum of all observations}}{\text{Total number of observation}}$

To get a grade of Upper C​, the average of the first five tests scores must be greater than or equal to 70 and less than 80.

$70 \leq \text{Average} < 80$

The fifth test counts as two​ tests.

Putting the values we get:

$70 \leq \dfrac{66 +74+71 + 81+ x}{6} < 80\\\\420 \leq 292 + x < 480\\420 -292 \leq x < 480 - 292\\128 \leq x < 188$

Thus, a score of greater than equal to 128 and less than 188 will get a grade of Upper C