In a simple pattern, if 5 students in Group A have an average score of 92 and 7 students in Group B have an average score of 80, what is the overall average score?

• A. 83.75
• B. 85.00
• C. 86.25
• D. 87.50

Answer: (B)

This question tests how to compute a weighted average when groups differ in size. Multiply each group’s average by how many students are in that group, then divide the total points by the total number of students.

Five students averaging 92 contribute 5 × 92 = 460 points. Seven students averaging 80 contribute 7 × 80 = 560 points. Combined points = 460 + 560 = 1020, and total students = 5 + 7 = 12. Overall average = 1020 ÷ 12 = 85.00.

Because the groups have different sizes, you must weight their averages by group size; treating them as equal would give (92 + 80)/2 = 86, which isn’t correct here.