The NASDAQ index has decreased by 70% since year 2000. How much should the index increase in order to gain the same value as in year 2000 ?
Pick.
A) 400 %  B) 80 %  C) 233 %  D) 60 %  E) none of the above

Rationale: let x be the index in the year 2000 . after the decrease it becomes 0.3 x now for 0.3 x to reach 1 x it has to raise by 0.7 x . the increase needs to be 0.7 x / 0.3 x * 100 = 233.3 % answer c
Answer: C