Calculate Class Size: Finding Total Students with Scores 85 and 92 Using Mean of 88.5

Question

In an exam, half of the students score 85 and the other half score 92. The average score on the test was 88.5.

How many students are in the class?

Step-by-Step Solution

To solve this problem, we'll first set up an equation representing the given situation:

  • Let n n represent the total number of students.
  • The number of students scoring 85 is n2 \frac{n}{2} , and the number scoring 92 is also n2 \frac{n}{2} .
  • The total sum of all scores is n2×85+n2×92\frac{n}{2} \times 85 + \frac{n}{2} \times 92.
  • Given that the average score is 88.5, set up the equation:
  • n2×85+n2×92n=88.5\frac{\frac{n}{2} \times 85 + \frac{n}{2} \times 92}{n} = 88.5

Simplify and solve the equation:

First, calculate the total score:

n2×85+n2×92=n2(85+92)\frac{n}{2} \times 85 + \frac{n}{2} \times 92 = \frac{n}{2} (85 + 92)

=n2×177=88.5×n = \frac{n}{2} \times 177 = 88.5 \times n

Now, set up the equation:

n×1772=88.5×n\frac{n \times 177}{2} = 88.5 \times n

Cancel n n from both sides (assuming n0 n \neq 0 ):

1772=88.5\frac{177}{2} = 88.5

The equation is inherently true, and n n cancels out, showing that n n could be any even and positive integer to satisfy the given conditions.

Therefore, the number of students in the class could be any even and positive integers.

Answer

The number of students in the class could be any even and positive integers.