LG Game 4 Question 20 Explanation, by LSATHacks
This question places lilies in bouquet 1. Whenever a question gives you a new rule, your first task is to think about how this affects the other rules.
Rule 4 says that if there are lilies, then there are roses:
Rule 1 says that bouquets 1 and 3 can’t share flowers. So bouquet 3 can’t have roses:
The next deduction is tricky. Bouquets 2 and 3 must share two flowers. So bouquet 3 needs at least one more flower. Who else can go in bouquet 3? T and P are left. We can either place:
- P, or
- T and P (rule 5: if there’s T, there’s P).
So either way, bouquet 3 has P. B is CORRECT.
Graeme Blake / LSAT Hacks ,
I have studied a few questions and see that some require the use of the ‘contrapositive’ – sometimes inferred and sometimes not .
I have also found , similar to this question , that there are questions that do not automatically use the ‘contrapostive’ when one might make that assumption .
Can you please explain an indicator for when and when not to use the ‘contrapositive’? I thought that this would be a question where because T = P , that the inverse would likely be correct , P = T .
I’m not sure that’s the contrapositive. Contrapositive is just another way of framing what’s true.
Like if I say “this pet is a cat” and I say “cats are not dogs” then we can conclude that this pet is not a dog.
What happens if we have a dog? You probably know intuitively it is not a cat. That’s by taking the contrapositive and saying “if something is a dog it isn’t a cat”
But the question isn’t whether you do a contrapositive or not or where you can do it. A contrapositive of a conditional statement is *always* valid, and it’s just something you need to know is true.