*Directions: Solve each problem and choose the correct answer.*

On the first 5 of 6 semester tests, each of which is worth 100 points, a student has earned the following grades: 75, 87, 83, 89, and 94. What score must the student earn on the sixth 100-point exam to earn an average test grade of 89 for all 6 tests?

A. 86

B. 89

C. 94

D. 99

E. The student cannot earn an average of 89.

## Knowsys Method

**Read the problem carefully.** Be sure to keep the numbers in this problem straight so that you do not make any careless mistakes in your work.

**Identify the bottom line. ** last score needed so that average of 6 is 89?

**Assess your options. **You could sub in the different answers for the 6th test score or you could leave the missing number as a variable. Either way, you need to use the "average formula," which you should definitely memorize. Every time you see the word "average" on the exam, you should immediately think: "average = the sum divided by the number." Let's use that formula to solve this problem quickly and easily.

**The Average Formula**

**Attack the problem.**

We are looking for the 6th test, which is part of the sum. Here's what we are given:

All we have to do now is solve for x.

89 * 6 = 428 + x

534 = 428 + x

106 = x

Hmmm. Since the test is only worth 100 points, can the student earn a 106? Nope. So, our answer is E.

**Loop back. **Verify that you solved for the bottom line.

The correct answer is **E**.

**Level = Medium **

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