Critical reasoning GMAT – The percentage Trap

Critical reasoning GMAT – The percentage Trap

 

Lets try and solve an official Critical reasoning question first :

In the United States, of the people who moved from one state to another when they retired, the percentage who retired to Florida has decreased by three percentage points over the past ten years. Since many local businesses in Florida cater to retirees, this decline is likely to have a noticeably negative economic effect on these businesses.

Which of the following, if true, most seriously weakens the argument?

  1. Florida attracts more people who move from one state to another when they retire than does any other state.
  2. The number of people who move out of Florida to accept employment in other states has increased over the past ten years.
  3. There are far more local businesses in Florida that cater to tourists than there are local businesses that cater to retirees.
  4. The total number of people who retired and moved to another state for their retirement has increased significantly over the past ten years.
  5. The number of people who left Florida when they retired to live in another state was greater last year than it was ten years ago.

On the GMAT Critical reasoning section , you will see a lot of questions similar to the one given above. So how do you go about solving such question which involve percentages ???

Percentages can be deceiving and it can actually play havoc if one does not play attention to detail to such questions.

One of the safest ways to go about solving such questions involve taking a  Hypothetical number and then converting  the percentage given in the question to actual numbers.

For example in this particular case let’s assume some numbers

Percentage of people who retired and came to Florida 10 years ago – 10%.

Percentage of people who retire and come to Florida now – 7%

Since we have to weaken the conclusion that the Revenue has decreased over the last 10 years for the local businesses in Florida , we can take some numbers that can actually prove this weakness.

Suppose there were 1000 people who retired 10 years back and moved – 10% of those came to Florida – i.e 100 people came to Florida after their retirement.

The number of people who retire now – (we should take a significantly greater number than the one taken above in order to prove the weakness) – Let’s assume the number of retirees to be 5000. 7% of this is 350.

100 – 350 -> That’s an increase in businesses !!!!

This means that even though the percentage of people who retire and come to Florida has decreased but the absolute number of number who come to Florida after retirement has increased significantly and hence there should be no economic loss to local businesses.

With this in mind let’s see the answer choices and try and eliminate the incorrect answer choices.

  1. Florida attracts more people who move from one state to another when they retire than does any other state – > This option is irrelevant as we need to look into people who move into Florida and not the ones who are outside of the state.
  2. The number of people who move out of Florida to accept employment in other states has increased over the past ten years -> Again irrelevant for the same reason as for A.
  3. There are far more local businesses in Florida that cater to tourists than there are local businesses that cater to retirees -> Irrelevant because the comparison is not between local businesses that cater to different businesses.
  4. The total number of people who retired and moved to another state for their retirement has increased significantly over the past ten years -> This is bang on with our analysis -> Correct.
  5. The number of people who left Florida when they retired to live in another state was greater last year than it was ten years ago -> This if any strengthens the passage instead of weakening it.

 

However also be aware that converting percentages to numbers may not always be a good idea but it can actually help you sometimes so one has to be careful while applying this method.

Let us know if you have any doubt in this question or need help  regarding GMAT preparation.

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