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0 / 60 seg.
There was a small get-together. There were a total of 28 handshakes exchanged between the guests. How many guests were present?
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8
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2
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1
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2
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3
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3
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3
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6
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Clue
THERE WERE 8 GUESTS. IF THERE ARE 2 GUESTS, THERE WILL BE 1 HANDSHAKE. SO, 2 GUESTS, 1 HANDSHAKE 3 GUESTS, 2 HANDSHAKES 3 GUESTS, 3 HANDSHAKES 4 GUESTS, 6 HANDSHAKES WITH THIS, FOR N GUESTS, WE WILL HAVE (N(N-1))/2 HANDSHAKES
THEY ARE 10.5 AND 0.5 YEARS OLD. A COMMON WRONG ANSWER IS 10 AND 1. THIS IS WRONG BECAUSE THE DIFFERENCE IN AGE WOULD BE 9, NOT 10
THE PROBABILITY IS 1/2. THERE ARE INITIALLY 4 POSSIBILITIES: GIRL-GIRL, GIRL-BOY, BOY-GIRL AND BOY-BOY. SINCE THE OLDER CHILD IS A BOY, WE CAN RULE OUT THE GIRL-GIRL AND GIRL-BOY COMBINATIONS
THE NEXT NUMBER IN THE SEQUENCE IS 1113213211. EACH NUMBER DESCRIBES THE PREVIOUS NUMBER. STARTING WITH 1, THE SECOND NUMBER DESCRIBES IT AS 11 (ONE 1). THEN THE THIRD NUMBER DESCRIBES 11 AS 21 (TWO 1'S). THEN THE FOURTH NUMBER DESCRIBES 21 AS 1211 (ONE 2, ONE 1). TO DESCRIBE 13112221, IT HAS TO BE 1113213211 (ONE 1, ONE 3, TWO 1, THREE 2, ONE 1). IN MATHEMATICS, THIS IS CALLED THE LOOK-AND-SAY SEQUENCE
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