Calculating a Weighted Average
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The following table demonstrates how a weighted grade is calculated. The percentage in each category is multiplied by its respective weight. The sum of these contributions is the total grade percentage.

Category Name Percentage in Category   Weight of Category Contribution
Homework 93% × .30 0.279
Quiz/Test 88% × .50 0.440
Exam 91% × .20 0.182
  .901
Total 90.1%

The question that often arises is "What must I get on the final exam to bring my grade to a certain level?" Let us represent the above table as an algebraic expression using h, q, and e to represent the categories: homework, quiz/test, and exam respectively. This is done as follows: h*the weight of h + q*the weight of q + e*the weight of e = final grade. To solve for the grade on the exam, enter in the available information with x representing the grade on the final exam and the desired grade for the class. The following is an example.

Category Name Percentage in Category   Weight of Category Contribution
Homework 95% × .30 0.285
Quiz/Test 86% × .50 0.43
Exam ? × .20 ?
Total 90%

Mathematically this problem can then be solved as follows.

h*(the weight of h) + q*(the weight of q) + e*(the weight of e) = final grade

(.95)*(.30) + (.86)*(.50) + x*(.20) = .90

.285 + .43 + .2x = .90

.715 + .2x = .90

.2x = .90 - .715

.2x = .185

x = .185/.2

x = .925

92.5%

This grade calculator can help to calculate your grade or the grade you need to get on a test or final.


Last updated: 5/11/11 Submit comments here