The average weight of the boys in a class is 68.5kg and that of the girls in the same class is 57.5 kg. If the average weight of all the boys and girls in the class is 65.2 kg. then the percentage of the number of boys in the class is?

70%

                       Boys    :     Girls

Average ⇒     68.5            57.5

                              65.2

No.        ⇒     7.7       :       3.3

                       7        :        3       =    10 (total)

Percentage of Boys = \(\frac{7}{10}\) × 100 = 70%