contestada

In a class in which the final course grade depends entirely on the average of four equally weighted 100-point tests, David has scored 76
, 80
, and 84
on the first three. What range of scores on the fourth test will give David a C for the semester (an average between 70
and 79
, inclusive)? Assume that all test scores have a non-negative value.

Express your answer in interval notation.

Respuesta :

loopygames18p40ojf

Answer: [40, 76]

Step-by-step explanation:

First you should set up an equation like this

76 + 80 + 84 + x = 70*4 and

76 + 80 + 84 + y = 79*4. Solving both of these will give you the endpoints of the interval you need. Solving for x you get 280-84-80-76= 40. For y you get 316-84-80-76= 76. You should see these and think that they are reasonable answers because his average grade currently is higher than a C, so he would have to do worse for the average grade to go down to a C.

To put it in interval notation, it should be [40, 76]. The [ brackets are because it includes the endpoints.

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