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December 2016 LSAT
Last year, a software company held a contest to generate ideas for their new logo. According to the rules, everyone w...
on November 11 at 10:24PM
Hello, Why is the answer about necessary.
on November 12 at 03:12AM
Let's identify the sufficient and necessary conditions in the second sentence.
If someone entered the contest (EC), then they received a T-Shirt (TS).
EC - - - - - - - - - - > TS
This allows us to create a contrapositive. If someone did not win a T-shirt, then they did not enter the contest. We can say this for certain. If the necessary condition fails, then so does the sufficient condition.
not TS - - - - - - - - -> not EC
Now, let's evaluate the conclusion. Juan has a T-shirt with the company's new logo, so he must have entered the contest.
TS - - - - - - - - - > EC is not valid.
We cannot simply reverse our sufficient and necessary conditions. It takes on an entirely new meaning. It states that Juan owning the T-shirt proves that he entered the contest. However, there could be a number of ways to acquire a T-shirt. Maybe Juan bought it, or maybe it was given to him by someone who entered the contest. This is why B is the correct answer. The author concludes that entering the contest is a necessary condition, when the premise indicates that it is sufficient.
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