A student scores 80, 85, and 90 in three tests. What score does he need in the fourth test to have an average of 85?

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Q: A student scores 80, 85, and 90 in three tests. What score does he need in the fourth test to have an average of 85?

Solution: Let the fourth score be x. (80 + 85 + 90 + x) / 4 = 85. Solving gives x = 95.

Steps: 7

Step 1: Add the scores of the first three tests: 80 + 85 + 90.
Step 2: Calculate the total from Step 1: 80 + 85 + 90 = 255.
Step 3: Let the score needed in the fourth test be x.
Step 4: Write the equation for the average: (255 + x) / 4 = 85.
Step 5: Multiply both sides of the equation by 4 to eliminate the fraction: 255 + x = 340.
Step 6: Subtract 255 from both sides to solve for x: x = 340 - 255.
Step 7: Calculate the value of x: x = 85.