In a class of 45 students, there are 20 girls who scored an average of 42 marks in a test of 50 marks. If the class average is 36, what are the average marks of the boys?

32.50 32.10 30.80 31.20

31.20

Number of boys = 45 - 20 = 25 Let average marks of boys = B ATQ, 20×42 + 25×B = 45× 36 840 + 25B = 1620 25B = 780  B = 31.2 So , average of boys = 31.20