Sandy buys an old scooter for $900 and spends $300 on its repairs. If Sandy sells the scooter for $1500, what is the gain percent?  Select the correct option
A) 10 %
B) 15 %
C) 20 %
D) 25 %
E) 30 %

Rationale: "selling price / total cost = 1500 / 1200 = 1.25 the gain percent is 25 % . the answer is d ."
Answer: D