A student scored 60, 70, and 80 in three subjects. If he wants to achieve an average of 75, what score does he need in the fourth subject? (2023)

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Q: A student scored 60, 70, and 80 in three subjects. If he wants to achieve an average of 75, what score does he need in the fourth subject? (2023)

Solution: Let the score in the fourth subject be x. The average is (60 + 70 + 80 + x) / 4 = 75. Solving gives x = 85.

Steps: 8

Step 1: Add the scores of the first three subjects: 60 + 70 + 80.
Step 2: Calculate the total from Step 1: 60 + 70 + 80 = 210.
Step 3: Let the score in the fourth subject be x.
Step 4: Write the formula for the average of four subjects: (210 + x) / 4.
Step 5: Set the average equal to 75: (210 + x) / 4 = 75.
Step 6: Multiply both sides of the equation by 4 to eliminate the fraction: 210 + x = 300.
Step 7: Subtract 210 from both sides to solve for x: x = 300 - 210.
Step 8: Calculate the value of x: x = 90.