2011-01-07, 02:25 AM
100%. If you flip 2 coins...
HH
HT
TH
TT
Technically speaking, it's impossible for TT to never occur with a normal coin. For it to never occur, there must be no Tails side at all (or have the coins be biased to always show Heads). Therefore, by eliminating all "Tails" results from the list of possibilities, the only possible combination left is HH. Thus, the probability of obtaining 2 Heads is 100%.
HH
HT
TH
TT
Technically speaking, it's impossible for TT to never occur with a normal coin. For it to never occur, there must be no Tails side at all (or have the coins be biased to always show Heads). Therefore, by eliminating all "Tails" results from the list of possibilities, the only possible combination left is HH. Thus, the probability of obtaining 2 Heads is 100%.