If john makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person. If there were 6 other contributions made before john's, what is the size of his donation? Options.
A) $ 225  B) $ 150  C) $ 200  D) $ 250  E) $ 450

Rationale: "cavg = average contribution before john cavg * 1.5 = 75 , therefore the average cont is $ 50 before john . if he needs to increase the average contribution by $ 25 , he must put in $ 25 for each of the 6 people . so $ 150 . but , he also has to put in the average for himself ( the seventh person ) , so add $ 75 . so $ 225 is your answer . answer a"
Answer: A