PSAT Math Multiple-Choice Question 821: Answer and Explanation

Question: 821

Look at how many of the particular item Stores A and B sold at the presale price. What is the arithmetic mean of this set of values to the nearest tenth?

• A. 8.1
• B. 9.7
• C. 10.5
• D. 12.8

Correct Answer: D

Explanation:

(D) The arithmetic mean is the average. Solve this problem using a weighted average. In other words, calculate the average by factoring in the relative amounts sold of the item by each store.

Store	Price Before Sale	Quantity Sold Before Sale	Sale Price	Quantity Sold After Sale
Store A	$12.50	350	$11.00	400
Store B	$13.25	260	$10.00	520
Store C	$11.75	550	$9.50	625
Store D	$14.00	220	$10.25	460

Store A sold 350 items for $12.50 each, and Store B sold 260 items for $13.25 each. The total number of items sold is 350 + 260. You can compute the average as follows: