Correct Answer - Option 1 : 9.5
Calculation:
⇒ Let be assume the score of the boy is x and the score of the girl is y.
⇒ According to question,
⇒ (y/30) - (x/20) = 5
⇒ Average of class = (x + y)/50
⇒ Let be assume new score of boys and girls is x' and y' respectively.
⇒ y/30 - y'/30 = 3
⇒ (x' + y')/50 - (x + y)/50 = 2
⇒ y' = y - 90
⇒ By solving we get x' = x + 190
⇒ New average of boys = (x + 190)/20 = x/20 + 9.5
⇒ The average increase by 9.5.
∴ The required result will be 9.5.