2011-01-08, 03:52 AM
When you flip two coins here are all of the possibilities:
HH
TH
HT
TT
Case1: If you only know that one of them is Heads (but not which one), then you're left with:
HH
TH
HT
Thus P(HH)=1/3.
Case2: If you know WHICH of the coins is heads (say, the one on the left) you're left with:
HH
HT
Thus P(HH)=1/2.
In this problem, however, we're told that 1 of them is heads and not told which one... thus it's the case above and the answer is 1/3. So yeah... the wording makes a difference if you happen to know WHICH is heads, or if you just dont know.
HH
TH
HT
TT
Case1: If you only know that one of them is Heads (but not which one), then you're left with:
HH
TH
HT
Thus P(HH)=1/3.
Case2: If you know WHICH of the coins is heads (say, the one on the left) you're left with:
HH
HT
Thus P(HH)=1/2.
In this problem, however, we're told that 1 of them is heads and not told which one... thus it's the case above and the answer is 1/3. So yeah... the wording makes a difference if you happen to know WHICH is heads, or if you just dont know.