Question

Grading Scale 2 has the following weights- Tests- 60% Quiz- 15% Homework- 10% Final Exam- 15% What do you need to score on the Final Exam to make an 78 in the class if your grades are- Show steps. Test Grades- 85 Quiz- 87 Homework- 68 Final Exam- ??

a. 85(60) + 87(15) + 68(10) + X(15) = 78 X = 49.33


b. 85(6.0) + 87(1.5) + 68(1.0) + X(1.5) = 78 X = 53.62


c. 85(.60) + 87(.15) + 68(.10) + X(.15) = 78 X = 47.67


d. 85(.60) + 87(1.5) + 68(.10) + X(1.5) = 78 X = 35.59

Answer 1

c. 85(.60) + 87(.15) + 68(.10) + X(.15) = 78; X = 47.67

Explanation:

The weighted average is the sum of products of score and weight. Choice C has the percentage weights properly expressed as decimal values.

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The other equations could work if the final score of 78 were weighted by the corresponding equivalent of 100%. (X is wrong in the other choices as well.)

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The attachment shows the "work". Given that choice C is the only correct equation, we presumed that the value of X was correct. The equation solver confirms this. If you want to do it by hand, compute the sum of products, subtract that sum, then divide by 0.15.

X = (78 -70.85)/.15 = 7.15/.15 = 47 2/3