The stock market index decreased this month by one-thirteenth of last month's index. If this month's index is 2,400, what was last month's index?
A) 2,585
B) 2,320
C) 2,483
D) 2,600
E) 2,215

Question

Quizplus · Accepted Answer

The decrease was one-thirteenth of last month's index, so this month's index is 12/13 of last month's index. To find last month's index, divide this month's index by 12/13: 2400 / (12/13) = 2600.

The Stock Market Index Decreased This Month by One-Thirteenth of Last