Exactly 18 months ago management in a certain retail electronics store

Bunuel - when working with percent increase we usually take the rate + rate*(%increase). (for example if the interest rate is increased by 5% we dont simply add 5% to it). Why can we use the linear equation here. The language to me seems to indicate that we should take the original rate*(1.005)^n where n is the number of months from the origination of the pattern.

Thanks!

sninja Interesting question. Note that on the actual test, you want to get in the habit of immediately glancing at the answer choices and noticing that all of them are linear, and not spend time or energy asking yourself questions like this. (I often see students asking themselves similar questions on SC, wondering whether something that "sounds off" is correct, but all of the answer choices have the same issue so it doesn't matter.)


The wording here is "The PERCENTAGE (of customers who appeared to be showrooming) increased by 0.5% each month."

This wording, in which the subject is "percentage" and verb is "increased", means we are ADDING to the percentage value itself; it's not compound exponential growth.

Alternatively, if the wording said "The NUMBER of customers increased by 50% each month", it would mean compound exponential growth.


Here are two other good official examples, one that uses addition, and one that uses compound exponential growth:

https://gmatclub.com/forum/each-year-fo ... l#p1102575

https://gmatclub.com/forum/when-a-certa ... ml#p811565

The question is very easy , once you understand it .
But the language here is wrong ,

"The results of the observations were that the percentage of customers who appeared to be showrooming increased by 0.5% each month."

Should be

"The results of the observations were that the percentage of customers who appeared to be showrooming increased by 0.5 each month."

That % sign makes it Geometric progression question rather than Arithmetic progression question....

I agree, this question is poorly worded.

­Hello GMATCoachBen !

I concluded with B, following this line of thought. Please help me identify the mistake. We know that the showrooming percentage increases by 0.5% per month. This can be represented as 0.5x, where x is the number of months. We also know that 10 months ago (x = 10), the showrooming percentage was 10.5%. So, we need to add a constant value (y) to 0.5x to get 10.5 when x = 10.

p = 0.5x + y

Now, we can plug in the values we know:

• p = 10.5
• x = 10

10.5 = 0.5(10) + y => 10.5 = 5 + y => y = 5.5­