Q19

[ManhattanPrepLSAT1]

[CissyM281]

Can you explain this please?

[ohthatpatrick]

If we're trying to max out the IN column, then lets look at any "troublemakers" we have that like to kick things into the OUT column.

Once we find one, we figure out
1. what's the max we could have IN when the troublemaker is IN
2. what's the max we could have IN when the troublemaker is OUT

The biggest troublemaker here is Music, who kicks out three things: Phys, Theater, and History.

1. If Music is in, then three things are already out, so our maximum at that point is four.

We could check whether that's even legal:
if P, T, and H are out, could we have L, M, S, and W all in?

No ... if W is in, S is out. If S is in, W is out. (rule 3)

So with M in, the best we could do would be three things IN.

---------------------------

2. If Music is OUT, nothing immediately happens. So could we put the other six people IN?
H, L, P, S, T, W ....... M?

No, because rule 1 and rule 3 are being broken.

Who's the biggest troublemaker from those rules?
W is, because it would kick P and S out.

So what if we throw out W. Can we put the rest in?
H, L, P, S, T ....... M, W

No, because rule 1 is still mad. We can't have both H and S. We can only have one of them.
How about this?
L, P, T, H/S ........ S/H, M, W

Yes, this works. So the max we can do is four.



=========

If you know how to do placeholders in In/Out games, then you're original master diagram would have looked like this:

__ __ __ + ........ H/ST .... M/PT .... W/PS
....IN..............................OUT

Rule 1 tells us that "at least H or the pair of ST will always be OUT"
Rule 2 tells us that "at least M or the pair of PT will always be OUT"
Rule 3 tells us that "at least W or the pair of PS will always be OUT"

So if you're using placeholders, you already know there's a minimum of three things out
(H, M, W is the easiest way to see how we could only have three out)

Thus, you'd just verify whether you could really get away with having the other four in:
L, P, S, T .......... H, M , W

Since that works, you'd know that four is the max we can do.

Hope this helps.

[AlizaS645]

For the placeholders, why does it mean that (for example) H is out or the PAIR S/M are both out.

If H is in then both S& M are out. But let's say H is out, couldn't M or S be out also?

[smiller]

For the placeholders, why does it mean that (for example) H is out or the PAIR S/M are both out.

If H is in then both S& M are out. But let's say H is out, couldn't M or S be out also?

That's correct. On the LSAT, the word "or" is not exclusive unless that is specifically stated. To use a simpler example, let's consider a rule that states, "if H is in then M is out," The contrapositive is, "if M is in then H is out." In this case it would be accurate to say, "either M or H must be out." It's also true that M and H can both be out. The original rule only applies if H is in, and the contrapositive only applies if M is in. Nothing is triggered by H or M being out.

When we, or the LSAT, state something like, "either H or M must be out," it's possible for both to be out. If it's not possible, that would be explicitly stated: "either H must be out or M must be out, but not both."

Going back to your example:

If H is in then both S& M are out. But let's say H is out, couldn't M or S be out also?

This is the same situation. The original rule is only triggered if H is in. The contrapositive is only triggered by S or M being in. Nothing is triggered by something being out. So it's true that, H, S, and M could all be out.

Going back to the original statement that you asked about:

H is out or the PAIR S/M are both out.

When we use "or" this way, it doesn't preclude H, S, and M from all being out. It just means that either one situation OR the other must happen.

I hope this helps!