In a class of 60 students, 40% are girls. The average of the girls marks is 45 and that of the boys is 75. What are the average marks of the whole class?

65 70 68 63

63

Ratio ⇒ Boys     :         Girls                 3        :          2  Avg marks of class = \(\frac{3 × 75 + 2 × 45}{3 + 2}\)                             = \(\frac{225 + 90}{5}\) = \(\frac{315}{5}\)  = 63