swerve wrote:What percentage of his bills did Stanley pay before their due dates last month?

1) Last month Stanley would have paid 70 percent of his bills before their due dates if he had paid 40 percent more bills than he actually did.
2) Last month the ratio of total bills to bills paid before their due dates was 2:1.

The OA is D

Source: Princeton Review

Target question: What percentage of his bills did Stanley pay before their due dates last month?
This is a great candidate for rephrasing the target question.
Aside: We have a free video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100

Let P = # of bills PAID before due date
Let T = TOTAL # of bills

IMPORTANT: If we can determine the ratio P/T then we can calculate the required percent. For example, if P/T = 3/4, then Stanley paid 75% of his bills.
So, we can rephrase the target question as....
REPHRASED target question: What is the value of P/T?

Statement 1: Last month Stanley would have paid 70 percent of his bills before their due dates if he had paid 40 percent more bills before their due dates than he actually did.
If Stanley had paid 40 percent more bills before their due dates than he actually did, then he would have paid 1.4P bills.
We're told that this would have resulted in Stanley paying 70% (i.e., 7/10) of his bills.
So, we can write 1.4P/T = 7/10
If we take this equation and divide both sides by 1.4, we get P/T = 1/2
Since we can answer the REPHRASED target question with certainty, statement 1 is SUFFICIENT

Aside: This means that Stanley paid 50% of his bills on time.

Statement 2: Last month the ratio of total bills to bills paid before their due dates was 2 : 1
In other words, T/P = 2/1
Or we can write: P/T = 1/2
Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT

Answer: D
Cheers,
Brent