Multiple choice

\text{The average marks obtained by all student in a class is 75.5. Average marks of boys is 70 and the average marks of total girls is equal to number of boys in class. Find the number of students in class.}

  1. 55

  2. 45

  3. 85

  4. Can't be determine.

  5. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let number of boys be b and girls be g. Total average: (70b + ag)/(b+g) = 75.5, where a = girls' average marks = number of boys = b. So (70b + bg)/(b+g) = 75.5. This simplifies to b(70+g) = 75.5(b+g). We have two variables but one equation, so b and g cannot be uniquely determined.

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