The mean of five numbers is . Four of the numbers are . What is the fifth number?

Answer and explanation

Correct answer: C. 28

  1. Step 1: Determine the total sum needed: .
  2. Step 2: Find the sum of the four given numbers: .
  3. Step 3: Subtract from the total to find the missing value: .
Answer
28.
Why not the others: - 24 is the mean of the numbers. - 33 adds rather than subtracts the constant term in the final step in . - 23 omits the factor of 2 in the denominator during simplification.

Practise more Statistics and probability.

Free questions with an explanation for every one, and full timed ACT mock tests.