MathDB
Problems
Contests
National and Regional Contests
China Contests
ASDAN Math Tournament
2017 ASDAN Math Tournament
23
23
Part of
2017 ASDAN Math Tournament
Problems
(1)
2017 Guts #23
Source:
11/25/2022
Ben creates an
8
×
8
8\times8
8
×
8
grid of coins, where each coin faces heads with probability
1
2
\tfrac{1}{2}
2
1
, and tails with probability
1
2
\tfrac{1}{2}
2
1
. Ben then makes a series of moves; each move consists of selecting a coin in the grid and flipping over all coins in the same row and column as the selected coin. Suppose that in Ben’s current grid of coins, it is possible to make a series of moves so that all coins in the grid are heads, and that Ben will make the fewest number of moves to do so. What is the expected number of moves that Ben makes?
2017
Guts Round