Please see the question to the Preplounge community below.

*QUESTION:*

*James is able to sell 15 of product A and 16 of the product B a week, Sally is able to sell 25 of product A and 10 of the product B a week, and Andrew is able to sell 18 of the product A and 13 of the product B a week. If product A sells for $35.75 each and product B sells for $42.25 each, what is the difference in the amount of money earned between the most profitable and the least profitable seller?*

*ANSWER*

*James’s profit: 35.75 ∙ 15 + 42.25 ∙ 16 = 536.25 + 676 = 1212.25$.*

*Sally’s profit: 35.75 ∙ 25 + 42.25 ∙ 10 = 1316.25$.*

*Andrew’s profit: 35.75 ∙ 18 + 42.25 ∙ 13 = 1192.75$.*

*Thus, the most profitable seller is Sally, and the least profitable is Andrew**.*

*Th**e difference between their profits is 1316.25 − 1192.75 = 123.5.*

**AND NOW THE QUESTION TO COMMUNITY:**

To answer this question we have to make 10 operations. And all this in 80 seconds - i.e. understand the questions and make 10 operations, which leaves less than 8 seconds per operation. How to solve this question faster? Any ideas?

If there's no shortcut, can you share the sources to improve math?