Data Sufficiency

VJesus12 wrote: ↑

Fri Feb 11, 2022 3:40 am

At the beginning of last month, a stationery store had in stock 250 writing pads, which had cost the store $0.75 each. During the same month, the store made only one purchase of writing pads. What was the total amount spent by the store on the writing pads it had in stock at the end of the month?

(1) Last month the store purchased 150 writing pads for $0.80 each.
(2) Last month the total revenue from the sale of writing pads was $180

Answer: E

Source: GMAT Prep

Given: At the beginning of last month, a stationery store had in stock 250 writing pads, which had cost the store $0.75 each. During the same month, the store made only one purchase of writing pads

Target question: What was the total amount spent by the store on the writing pads it had in stock at the end of the month?

Statement 1: Last month the store purchased 150 writing pads for $0.80 each.
Since we have no information about the number of writing pads purchased by the store's customers, there's no way to determine the number of writing pads the store had in stock at the end of the month.
Statement 1 is NOT SUFFICIENT

Statement 2: Last month the total revenue from the sale of writing pads was $180
Here, we don't have any information about the number of writing pads the store purchased at some point during the month.
So, there's no way to determine the number of writing pads the store had in stock at the end of the month.
Statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
The combined statements are still NOT SUFFICIENT.
There are two big issues with statement 2.
First, since we don't know the retail price of each pen, there's no way to determine the number of pens that customers purchased.
For example, if the store charges $180 per pen, then only 1 pen was sold, which means there were 399 pens remaining at the end of the month.
If the store charges $10 per pen, then 18 pens were sold, which means there were 382 pens remaining at the end of the month.
And so on.

Second, even if we knew the exact price the store charges per pen, we still wouldn't have enough information, because we wouldn't know how many of the pens purchased were $0.75 pens and how many were $0.80 pens.
For example, if the store charges $1.80 per pen, then the store sold 100 pen's last month, but we don't know the breakdown of $0.75 pens and $0.80 pens.

For the these two very big reasons, the answer is E