Asked by Katie

Using a standard deck of cards, find the probability that:

1) You choose two cards and one is a face card and the other is black

2) A black jack and then an ace are drawn

Answers

Answered by MathMate
I'll solve #2 first, where the two cards requested are mutually exclusive.
Since there are two black jacks, and 4 aces, we have
P(BJ,A)=2/52*(4/51)=8/2652=2/663

====================================

For problem #1, we denote the events as:
B=black card, B'=red card
F=face card, F'=non-face card

The possible successful outcomes can be split into two stages, first and second card, denoted by the couple ( , ).

First a face card then a black card:
P(B'F,B)=(6/52)(26/51) (red face,black)
P(BF,BF')=(6/52)(20/51) (black face, black non-face)
Note: (black face, black face) is included in the next case.
Then a black card followed by a face card:
(BF,F)=(6/52)(11/51) (black face,any face)
(BF',F)=(20/52)(12/51) (black non-face, any face)

All these add up to 97/442.

We can also calculate the unsuccessful outcomes and subtract from 1 to get the successful outcomes.

The unsuccessful outcomes are:
P(F',F')=(40/52)(39/52) (two non-face)
P(B',B')=(26/52)(25/52) (two reds)
P(BF,B'F')=(6/52)(20/52) (black face,red non-face)
P(B'F',BF)=(20/52)(6/52) (red non-face, black face)

Out of this, we have double-counted, and therefore should subtract
P(F'B',F'B')=(20/52)(19/51) (both cards red non face)

Summing them all up we get 345/442 for the probability of unsuccessful outcomes.
Subtract from 1 to get 97/442 as the probability of successful outcomes. This is the same probability as we calculated above.

There are no AI answers yet. The ability to request AI answers is coming soon!

Related Questions