Question

Out of 75 students in a class, 60% are boys and rest are girls. The average score of girls in a test is 40% more than that of boys. If the average score of all the students in the class is 58, then what is the average score of girls?
1. 67.2
2. 63.8
3. 70
4. 50

Answer 1

Correct Answer - Option 3 : 70

Given:

Total stundents = 75

60% are boys and rest are girls

Formula used:

Average = (Sum of Values/Number of Values)

Calculation:

According to the question:

Total boys in class = 75 × 60/100 = 45

Rest girls = 75 - 45 = 30

The average score of girls in a test is 40% more than that of boys

Average score of girls = 140/100 × Average score of boys

Average score of girls/Average score of boys = 7/5

Let the Average score of girls be 7x

And Average score of boys be 5x

Now,

58 = (7x × 30 + 45 × 5x)/75

⇒ 58 × 75 = 210x + 225x

⇒ 58 × 75 = 435x

⇒ x = (58 × 75)/435 = 10

Average score of girls = 7x = 7 × 10 = 70

∴ Average score of girls is 70.