A student scored 70, 80, and 90 in three exams. What score is needed in the four

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Question: A student scored 70, 80, and 90 in three exams. What score is needed in the fourth exam to achieve a mean of 85?

Options:

Correct Answer: 95

Solution:

Let the fourth score be x. Mean = (70 + 80 + 90 + x) / 4 = 85. Thus, 240 + x = 340, so x = 100.

A student scored 70, 80, and 90 in three exams. What score is needed in the fourth exam to achieve a mean of 85?

A student scored 70, 80, and 90 in three exams. What score is needed in the fourth exam to achieve a mean of 85?

Step 1: Add the scores of the first three exams: 70 + 80 + 90.
Step 2: Calculate the total of the first three scores: 70 + 80 + 90 = 240.
Step 3: Let the score needed in the fourth exam be represented as 'x'.
Step 4: Write the formula for the mean (average) of the four scores: (240 + x) / 4.
Step 5: Set the mean equal to 85: (240 + x) / 4 = 85.
Step 6: Multiply both sides of the equation by 4 to eliminate the fraction: 240 + x = 340.
Step 7: Solve for 'x' by subtracting 240 from both sides: x = 340 - 240.
Step 8: Calculate the value of 'x': x = 100.

Mean Calculation – Understanding how to calculate the mean (average) of a set of numbers.
Algebraic Manipulation – Using algebra to solve for an unknown variable in an equation.