#11 - Local, Must Be True

[Dave Killoran]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=13830)

The correct answer choice is (D)

The restriction in the question stem leaves Casey with only five shirt types to choose from:

J92_Game_#2_#11_diagram 1.png

There are a limited number of solutions at this point, and since Casey cannot purchase both a large shirt and a small shirt, each solution involves purchasing either two medium shirts, or all three medium shirts. If Casey must buy at least two medium shirts, then he must buy at least one from the group of the medium red shirt and medium blue shirt. Thus, answer choice (D) is correct.

If you are uncertain about answer choice (D), attempt to remove both the medium red shirt and medium blue shirt from consideration; at that point a viable group cannot be selected as only one shirt of each size remains.

[destaat]

The answer is (d) but I'm convinced its (c). Can someone help me figure out my mistake. Given the question and the rules I know that Casey will buy two medium sized shirts but doesn't that mean shell either buy a large or a small shirt. And where is the restriction coming from that she cannot have a medium yellow shirt?

Please Help! Thank you!

[Dave Killoran]

Hi A.T.,

No problem. The restriction in the question stem leaves Casey with only five shirt types to choose from:

SY MR MY MB LY

There are a limited number of solutions at this point, and since Casey cannot purchase both a large shirt and a small shirt, each solution involves purchasing either two medium shirts, or all three medium shirts. If Casey must buy at least two medium shirts, then he must buy at least one from the group of the medium red shirt and medium blue shirt. Thus, answer choice (D) is correct.

If you are uncertain about answer choice (D), attempt to remove both the medium red shirt and medium blue shirt from consideration; at that point a viable group cannot be selected as only one shirt of each size remains.

Please let me know if that solves it. Thanks!

[emma312]

Thank you for the reply. I have problem on this question as well.
Why must Casey choose from MR and MB? Can't he have one from either LY or SY, and then two from MY/MB/MR?

Thanks!

[Jon Denning]

Hey Emma,

Thanks for the question! Question 11 serves to further restrict both the Small and Large shirt color options: if a Small shirt is purchased it must be Yellow (not Red from rules, and not Blue from this question), and if a Large shirt is purchased it too must be Yellow (not Blue from rules, and not Red from this question).

So consider what that means. Casey can buy now at most either one Small or one Large. To buy two Smalls would require two colors so we don't duplicate a shirt, and only one color is now available for Small (Yellow). And the same is true of Large shirts. The implication then is that Casey must buy at least two Medium shirts! Now, we don't know which two Medium shirts Casey will pick--Blue, Red, or Yellow--but having to choose at least two means either red or blue will always be chosen. Perhaps both, but certainly at least one.

And that's what D tells us! Either a Medium Red or Medium Blue must be purchased. It could be that both are purchased, but we know with certainty that at least one of those two will be (if only one, the other Medium shirt would be Yellow).

Put another way: you mentioned that he must have at least two from MY/MB/MR. If that's the case, then no matter which two he chooses one of the two will always be either red or blue, and that satisfies answer choice (D).

Does that make more sense?

[emma312]

Thank you Jon! That's very clear and helpful!

[bella243]

I don't understand why she's have to choose between MR and MB. Why can't she buy MR and MY? The rules say that no two shirt types are allowed, defined as size AND color. So, MY is not the same type as LY or SY. Please do help me !

[Adam Tyson]

Your proposed solution includes a MR, bella243, which helps to prove the answer. Could you have come up with a solution in which Casey does not buy a MR and also does not buy a MB? The only remaining shirts would then be the three yellow shirts, and Casey cannot buy a small shirt and a large one. In order for Casey to buy three shirts, she has to buy at least one of the MR and MB, and perhaps both. The word "or" in the answer means "at least one," and it is true that Casey must buy at least one of those two shirts, because if she buys neither there is no viable solution.

To clarify, she does not have to choose between those two - she can buy them both. But she for sure has to buy at least one of them, or else there is no way to solve the game. That's what the question is asking for - a minimum requirement.