All the spades are taken out from a pack of cards. Fro these cards, cards are drawn one by one without replacement till the ace of spades comes. The probability that the ace comes in the 4th draw, is

Options

A. `(1)/(13)`
B. `(12)/(13)`
C. `(4)/(13)`
D. none of these

Answer

A

Explanation

Clearly,
Required probability
=Probability of getting 3 non-ace cards in first three draws and getting an ace in fourth draw
`=(.^(12)C_(3))/(.^(13)C_(3))xx(1)/(10)=(1)/(13)`