by noah Fri Mar 30, 2012 4:07 pm
Tackling this question requires understanding the chain in the initial set-up.
G --> P + F --> P - T --> H - L
So, for example, G triggers P, F, T, H and L. Thus, G triggers everyone being in.
You must also remember that we can either have everyone leave 1 message, or 5 people leave 1 message and 1 person leave 2 messages, or 4 people leave 1 message and 1 person leave 3 messages. Thus, we definitely need 4 people.
With that in mind, let's dive in, remembering that 4 answers must be true. Thus, we're trying to "break" these answers:
(A) Can we avoid L leaving a message? If so, we'd have to avoid triggering G, P and T. If we knock out 3, how do we get to 5 people leaving messages? We have to have an L in.
(B) This suffers from the same problem. To avoid triggering T, we can't have G or F in. That leaves us with 4 people. Not enough. We have to have a T in.
(C) This is exactly the same as (A). We'd have to leave out G, P and T. There's got to be an H.
(D) We could have G trigger P, F, T, H and L. No doubling up allowed in this scenario! Thus this doesn't have to be true.
(E) This is something we already figured out.
That clear it up?