The average score of 65 students in a test is 50 . The ratio of the number of boys to that of girls is 4 : 5 . The average score of the girls is 20% more than that boys. The average score of boys is?

45

 Ratio of no. of students

             Boys    :     Girls

                4      :       5

 Ratio of avg. score : 20% = \(\frac{1}{5}\)

  Ratio of score of ,   Boys    :     Girls

                                 5R    :      6R

According to question ,

(4 × 5R) + (5 × 6R) = 9 × 50

                       50R = 450

                          R = 9

Average score of boys = 5 × 9 = 45