T _ K _
T H _
F _ X
_ V _ R ,
R _ T _ R N
W _ T H
N _ T H _ N G .
G _
_ V _ R
W _ T H
_ N _
C H _ C K _ N ,
R _ T _ R N
W _ T H
T H _
F _ X .
G _
_ V _ R
W _ T H
T H _
S _ C _ N D
C H _ C K _ N ,
R _ T _ R N
W _ T H
N _ T H _ N G .
F _ N _ L L Y ,
T _ K _
T H _
F _ X
_ V _ R .
O R
L _ T :
M _ N
=
M
F _ X
=
F
C H _ C K _ N 1
=
C 1
C H _ C K _ N 2
=
C 2
T H _ S
_ S
H _ W
T H _ Y
C R _ S S
T H _
R _ V _ R :
M , F
→
←
M
M , C 1
→
←
M , F
M , C 2
→
←
M
M , F
→ Clue
LET M = MISSIONARY AND C = CANNIBAL. THIS IS HOW THEY CROSS THE RIVER: M,C → ← M C,C → ← C M,M → ← M,C M,M → NOW, THERE ARE 3 MISSIONARIES AND 1 CANNIBAL ON THE OTHER SIDE OF THE RIVER. THIS CANNIBAL CAN FETCH THE OTHER 2 CANNIBALS ONE BY ONE TAKE THE FOX OVER, RETURN WITH NOTHING. GO OVER WITH ONE CHICKEN, RETURN WITH THE FOX. GO OVER WITH THE SECOND CHICKEN, RETURN WITH NOTHING. FINALLY, TAKE THE FOX OVER. OR LET: MAN = M FOX = F CHICKEN1 = C1 CHICKEN2 = C2 THIS IS HOW THEY CROSS THE RIVER: M,F → ← M M,C1 → ← M,F M,C2 → ← M M,F → FIRST THE TWO SONS ROWED ACROSS THE RIVER AND ONE STAYED BEHIND WHILE THE OTHER RETURNED IN THE BOAT TO HIS FATHER. THE SON REMAINED BEHIND WHILE THE FATHER CROSSED THE RIVER. THEN THE OTHER SON BROUGHT BACK THE BOAT AND THE TWO BROTHERS ROWED OVER TOGETHER FIRST, TAKE THE SHEEP ACROSS, COME BACK AND THEN TAKE THE BUNDLE OF GRASS. SINCE THE SHEEP WILL EAT THE GRASS IF LEFT UNATTENDED, TAKE THE SHEEP BACK ACROSS AND THEN TAKE THE LION ACROSS. THEN TAKE THE SHEEP BACK ACROSS AND THEY ARE ALL UNHARMED