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 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 IMMEDIATELY AFTER THE GUARD GOES BACK TO HIS POST UPON CHECKING THE BRIDGE, YOU START TO CROSS THE BRIDGE. JUST BEFORE THE 6 MINUTES IS UP, TURN AROUND AND START WALKING BACK TOWARDS THE GUARD. THE GUARD WILL COME OUT AND NOTICE YOU AND ASSUME THAT YOU ARE A VISITOR COMING FROM THE OTHER SIDE OF THE BRIDGE. HE WILL GO BACK TO HIS POST SINCE HE WILL NOT TURN YOU AWAY UNTIL YOU REACH HIM. ONCE THE GUARD HAS GONE BACK, IMMEDIATELY TURN BACK AROUND AND WALK TO THE OTHER SIDE OF THE BRIDGE. SINCE YOU HAD WALKED ALMOST 6 MINUTES PREVIOUSLY, YOU WILL REACH THE OTHER END OF THE BRIDGE IN ABOUT 4 MINUTES TIME - BEFORE THE GUARD COMES OUT OF HIS POST AGAIN