Multiple choice

In a school, there are two sections, A and B, for Grade 7. In section A, the average percentage score for a test is 92, while in Section B, the average percentage score for the same test is 84. If the average score of all 40 students in the two sections is 89 percent, then how many students are there in section B?

  1. 10

  2. 12

  3. 15

  4. 20

  5. 25
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let n be the number of students in section B. Then 40-n is the number in section A. Weighted average: (92(40-n) + 84n) / 40 = 89. 3680 - 92n + 84n = 3560. 120 = 8n. n = 15.

AI explanation

Let the number of students in section A be x and section B be y. Using the weighted average formula, 92 times x plus 84 times y equals 89 times x plus y. This expands to 92x plus 84y equals 89x plus 89y. Simplifying this gives 3x equals 5y. We also know x plus y equals 40, so substituting y with 0.6x gives 1.6x equals 40, meaning x is 25. The number of students in section B is 40 minus 25, which is 15.

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