L _ T :
D _ D
=
F
( 1 )
M _ M
=
M
( 2 )
S _ N
=
S
( 4 )
D _ _ G H T _ R
=
D
( 5 )
T H _ S
_ S
H _ W
T H _ Y
C R _ S S
T H _
T _ N N _ L :
F , M
→
( 2 )
←
F
( 1 )
S , D
→
( 5 )
←
M
( 2 )
F , M
→
( 2 )
T H _
T _ M _
_ N
B R _ C K _ T S
( )
_ N D _ C _ T _
T H _
T _ M _
T _ K _ N
T _
C R _ S S
T H _
T _ N N _ L .
I F
Y _ _
S _ M
T H _ M
_ P ,
_ T
W _ L L
_ D D
_ P
T _
1 2
M _ N _ T _ S Clue
LET: DAD = F (1) MOM = M (2) SON = S (4) DAUGHTER = D (5) THIS IS HOW THEY CROSS THE TUNNEL: F,M → (2) ← F (1) S,D → (5) ← M (2) F,M → (2) THE TIME IN BRACKETS () INDICATE THE TIME TAKEN TO CROSS THE TUNNEL. IF YOU SUM THEM UP, IT WILL ADD UP TO 12 MINUTES LET: CAMPER 1 = C1 (1) CAMPER 2 = C2 (2) CAMPER 3 = C3 (5) CAMPER 4 = C4 (10) THIS IS HOW THEY CROSS THE BRIDGE: C1,C2 → (2) ← C2 (2) C3,C4 → (10) ← C1 (1) C1,C2 → (2) THE TIME IN BRACKETS () INDICATE THE TIME TAKEN TO CROSS THE BRIDGE. IF YOU SUM THEM UP, IT WILL ADD UP TO 17 MINUTES THE MOTHER WAS THE MURDERER. WE KNOW FROM (3) THAT THE YOUNGEST PERSON WAS NOT THE VICTIM, FROM (4) THAT THE YOUNGEST PERSON WAS NOT THE HELPER AND FROM (6) THAT THE YOUNGEST PERSON WAS NOT THE KILLER. THE YOUNGEST PERSON CAN ONLY HAVE BEEN THE WITNESS THEREFORE. WE CAN WORK OUT FROM (5) THAT THE FATHER WAS THE OLDEST, FROM (2) THAT THE YOUNGEST PERSON MUST HAVE BEEN THE DAUGHTER. THEREFORE THE NEXT TO THE YOUNGEST MUST HAVE BEEN THE SON AND THE NEXT TO THE OLDEST, THE MOTHER. FROM THE STATEMENTS, WE CAN SORT OUT THE MEMBERS BASED ON AGE, FROM OLDEST TO YOUNGEST AS: FATHER, MOTHER, SON, DAUGHTER. WE CAN COME TO THE FOLLOWING CONCLUSION: MOTHER - MURDERER FATHER - HELPER SON - VICTIM DAUGHTER - WITNESS FIRST, THE ONE MINUTE PERSON AND THE TWO MINUTE PERSON MUST CROSS THE BRIDGE, FOR A TOTAL OF TWO MINUTES. THEN THE ONE MINUTE PERSON SHOULD COME BACK WITH FLASHLIGHT - TOTAL OF THREE MINUTES. THE FIVE MINUTE PERSON AND THE TEN MINUTE PERSON CROSS TOGETHER NEXT, MAKING THE TOTAL THIRTEEN MINUTES. NOW THE TWO MINUTE PERSON GOES BACK AND (TOTAL NOW FIFTEEN MINUTES) AND GETS THE ONE MINUTE PERSON AND THEY CROSS TOGETHER BRINGING THE TOTAL TO SEVENTEEN MINUTES