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

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

Step-by-step 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