Caroline scored 85, 88, and 89 on three of her four history tests. If her average score for all tests was 90, what did she score on her fourth test?

Options

A. `90`
B. `93`
C. `96`
D. `98`

Answer

To find out what Caroline scored on her fourth test, we can follow these steps:

### Step 1: Understand the average formula
The average score is calculated by dividing the sum of all scores by the number of tests. In this case, Caroline has taken four tests.

### Step 2: Set up the equation
Let the score of the fourth test be \( x \). The scores of the first three tests are 85, 88, and 89. Therefore, the equation for the average score can be set up as follows:

\[ \text{Average} = \frac{\text{Sum of all scores}}{\text{Number of tests}} \]

Given that the average score is 90, we can write:

\[ 90 = \frac{85 + 88 + 89 + x}{4} \]

### Step 3: Calculate the sum of the known scores
First, we need to find the sum of the scores from the first three tests:

\[ 85 + 88 + 89 = 262 \]

### Step 4: Substitute the sum into the equation
Now, substitute the sum into the average equation:

\[ 90 = \frac{262 + x}{4} \]

### Step 5: Multiply both sides by 4 to eliminate the denominator
To eliminate the fraction, multiply both sides by 4:

\[ 90 \times 4 = 262 + x \]

This simplifies to:

\[ 360 = 262 + x \]

### Step 6: Solve for \( x \)
Now, isolate \( x \) by subtracting 262 from both sides:

\[ x = 360 - 262 \]

Calculating this gives:

\[ x = 98 \]

### Conclusion
Caroline scored **98** on her fourth test.

---