The average marks of 50 students in a class are 52. The average marks of boys and girls in that subject are 50 and 55, respectively. The number of boys in the class is :
Answer & explanation
Correct answer: option 3
Let the no. of boys in the class be X
The no. of girls in the class be (50 - X).
According to the questions,
55 × (50 - X) + (50 × X) = (50 × 52)
2750 - 55X + 50X = 2600
150 = 5X
X = 30
So, the number of boys = 30
∴ The number of boys in the class is 30.