LRB Workbook p.27

[Zarie Blackburn]

We recently received the following question from a student. An instructor will respond below. Thanks!

Hi I have 2019 lsat logical reasoning bible workbook. On page 27 question 4 regarding car dealerships and 20 vs 25 sale price. I can’t figure out why the answer is III not I.

[Adam Tyson]

I find that the simplest way to wrap my head around these sort of numbers and percentages questions is to supply numbers, and for me the easiest number to supply when dealing with a percentage increase or decrease is 100. So let's imagine the Cheetah was priced at $100 back in December, before all these price changes began.

In January, the price went up 25%, so the new price was $125. In February they put the car on sale and reduced THAT price by 20%. A 20% reduction from $125 brings the price down to...$100, right where we were back in December! Choice III is proven correct just by that simple math! (125 x .8 = 100)

You have to remember when combining percentages like that to go through it step by step. You cannot just take 20 away from 25 and come up with a 5% increase, because the second percentage is based on a different number than the first percentage.