A student scores 60, 70, and 80 in three subjects. If he wants an average of 75,

Practice Questions

Q1
A student scores 60, 70, and 80 in three subjects. If he wants an average of 75, what score does he need in the fourth subject?
  1. 70
  2. 75
  3. 80
  4. 85

Questions & Step-by-Step Solutions

A student scores 60, 70, and 80 in three subjects. If he wants an average of 75, what score does he need in the fourth subject?
Correct Answer: 90
  • 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 needed in the fourth subject be x.
  • Step 4: Write the formula for the average: (210 + x) / 4 = 75.
  • Step 5: Multiply both sides of the equation by 4 to eliminate the fraction: 210 + x = 300.
  • Step 6: Subtract 210 from both sides to solve for x: x = 300 - 210.
  • Step 7: Calculate the value of x: x = 90.
  • Average Calculation – Understanding how to calculate the average of a set of numbers and how to manipulate equations to find an unknown value.
  • Algebraic Manipulation – Using algebra to solve for an unknown variable in an equation.
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