A student scores 80, 90, and 70 in three subjects. What score does he need in th

A student scores 80, 90, and 70 in three subjects. What score does he need in the fourth subject to have an average of 85?

A student scores 80, 90, and 70 in three subjects. What score does he need in the fourth subject to have an average of 85?

Correct Answer: 100

Step 1: Add the scores of the first three subjects: 80 + 90 + 70.
Step 2: Calculate the total from Step 1: 80 + 90 + 70 = 240.
Step 3: Let the score in the fourth subject be x.
Step 4: To find the average of four subjects, use the formula: (Total of all scores) / (Number of subjects).
Step 5: Set up the equation for the average: (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.

Average Calculation – Understanding how to calculate the average of a set of numbers by summing them and dividing by the count.
Algebraic Manipulation – Using algebra to solve for an unknown variable in an equation.