Multiple choice

The average pass percentage of girls in class X examination in a school is 85% and that of boys is 83%. The average pass percentage of all boys and girls in class X of that school is 83.7%. Find the percentage of number of girls in class X of that school.

  1. 35%

  2. 30%

  3. 45%

  4. 40%
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A Correct answer
Explanation

Use weighted average formula: 83.7 = 85x + 83(1-x), where x is fraction of girls. Solving gives x = 0.35 or 35%. Girls are 35% of the class, making their higher pass percentage pull up the overall average.

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