Question

In a class in which the final course grades depends entirely on the average of four equally weighted 100 point test David has scored 81, 92, and 74 on the first three. What range of scores on the fourth test will give David a b for the semester ( an average between 80 and 89 inclusive) assume that all the test scores have a non negative value

Answer 1

The range of scores on the fourth test to give David a B grade for the semester is at least 73 but less than or equal to 89.

What is a range?

A range refers to the difference between the lowest and the highest score.

A range of scores gives two values, the lowest and the highest scores.

Data and Calculations:

Scores secured by David = 81, 92, and 74

Total scores in three exams = 247

The average score for a B grade is:

80  ≤  B grade  < 90      ["at least" means ≤]

Therefore,

80 ≤ (81 + 92 + 74 + x) / 4  < 89  [assume equal weights for exams]

80 ≤ (247 + x) / 4 ≤ 89  [add values]

320 ≤ (247 + x) ≤ 356   [multiply by 4, retains a sense of inequality]

73 ≤ x < 109                   [subtracting 247 retains a sense of inequality]

Since exams are graded on 100 points, David cannot score 109, so the upper limit is put at 89.

Thus, the exam grade in the fourth test must be at least 73 but less than or equal to 89 to get a B average.

Learn more about inequalities at https://brainly.com/question/11613554

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