Practice Final A4
Can anybody confirm if this is the answer for A4? 10 divided by 3x(10 C 2) +10
rahulchandrupatla: March 19, 2015, 5:18 p.m.
I actually got $\frac{10}{(10choose1)(3choose2)(27)+10}$ because you are choosing one value out of 10 (10choose1) and then you choose two colors for that value which is (3choose2)
Lilyhui: March 19, 2015, 5:22 p.m.
For the denominator where does the 27 come from? I split the denominator into two cases (two cards the same and three cards the same )
rahulchandrupatla: March 19, 2015, 5:26 p.m.
The 27 comes because we can choose any card that is not of the value that we choose. For example. Say that we chose the value 3. Then that last card CANNOT be a 3, which leaves 27 cards to be picked, so its (27choose1) which is 27
Lilyhui: March 19, 2015, 5:32 p.m.
Would that mean that the order you pick the cards matter? I got (10 C2) to pick two distinct values and (3C2) to pick the card that repeats.
rahulchandrupatla: March 19, 2015, 6:20 p.m.
I dont think it means the order matters, because it does not matter what card out of the other 27 you pick, i don't see how it could imply order. is the (3c2) from the three cards you have? but technically you haven chosen your third card yet.
andrearamirez: March 19, 2015, 7:26 p.m.
where does the +10 come from?
Lilyhui: March 19, 2015, 7:31 p.m.
+10 comes from the case where three cards are the same. You choose one distinct value (10C1) and the two other cards have to be the same as this value to their prob is 1*1.
Lilyhui: March 19, 2015, 7:31 p.m.
(10 C1)*1*1=10
andrearamirez: March 19, 2015, 8:30 p.m.
thank you!