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0 / 60 seg.
One out of 9 otherwise identical balls is overweight. How can it be identified after 2 weighings?
W
_
_
G
H
_
G
R
_
_
P
_
F
3
B
_
L
L
S
_
G
_
_
N
S
T
_
N
_
T
H
_
R
G
R
_
_
P
_
F
3
,
T
H
_
N
Y
_
_
'
L
L
K
N
_
W
W
H
_
C
H
G
R
_
_
P
_
F
3
C
_
N
T
_
_
N
S
T
H
_
H
_
_
V
Y
B
_
L
L
.
P
_
C
K
2
B
_
L
L
S
F
R
_
M
T
H
_
T
G
R
_
_
P
_
N
D
W
_
_
G
H
_
N
_
_
G
_
_
N
S
T
T
H
_
_
T
H
_
R
Clue
40 SOCKS. IF HE TAKES OUT 38 SOCKS, ALTHOUGH IT IS VERY UNLIKELY, IT IS POSSIBLE THEY COULD ALL BE BLUE AND RED. TO BE 100 PERCENT CERTAIN THAT HE ALSO HAS A PAIR OF BLACK SOCKS HE MUST TAKE OUT A FURTHER TWO MORE SOCKS
TAKE 6 BALLS AND SPLIT THEM INTO 2 GROUPS OF 3 BALLS EACH. USE THE SCALE TO WEIGH THE 2 GROUPS. IF ONE OF THE GROUPS IS HEAVIER THAN THE OTHER GROUP, PICK 2 BALLS FROM THE HEAVIER GROUP AND USE THE SCALE TO WEIGH THEM. IF THEY ARE EQUAL IN WEIGHT, THE OTHER BALL IN THAT GROUP IS THE HEAVY ONE. IF BOTH THE GROUPS ARE EQUAL IN WEIGHT, THEN PICK THE REMAINING 2 BALLS AND USE THE SCALE TO DETERMINE THE HEAVIER BALL
SPLIT THE BALLS INTO 3 GROUPS WITH 3 BALLS EACH. PICK 2 GROUPS AND USE SCALE TO DETERMINE WHICH GROUP CONTAINS THE HEAVY BALL. ONCE THE GROUP IS DETERMINED, PICK 2 BALLS AND USE THE SCALE. IF THEY ARE EQUAL, THE OTHER BALL IS THE HEAVY ONE
WEIGH A GROUP OF 3 BALLS AGAINST ANOTHER GROUP OF 3, THEN YOU'LL KNOW WHICH GROUP OF 3 CONTAINS THE HEAVY BALL. PICK 2 BALLS FROM THAT GROUP AND WEIGH ONE AGAINST THE OTHER
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