Probability – Probability of Getting One Card from Each Suit in a 4-Card Deal

probability

My simple easy homework question. Just needed some double check 😀

Deal 4 cards from a deck of 52 cards. What is the probability that we get one card from each suit?

My answer

First Draw: We can get any card, and the card's suit will be done. $Chance:1$

Second Draw: Now we need to get 1 of the 3 remaining suits. There are 51 cards left. $Chance:\frac{13+13+13}{51}$

Third Draw: Now we need to get 1 of the 2 remaining suits. There are 50 cards left. $Chance:\frac{13+13}{50}$

Fourth Draw: Now we need to get the last remaining suit. There are 49 cards left. $Chance:\frac{13}{49}$

$P($One card from each suit$)=1*\frac{13+13+13}{51}*\frac{13+13}{50}*\frac{13}{49}=0.1055$

My tutor is known for giving not-so straightforward questions, so I'm wondering if I need to consider another way, or I could be wrong. Any alternatives welcome too!

Best Answer

first draw: Pick any card, probabilty 1 you are still OK

second draw: you must pick from 39 cards that won't wreck your hand out of 51 cards

third draw: you must pick from 26 of the remaining 50

fourth draw: you mustpick from 13 of the remaining 49.

Altogether, you get a probability of

$$1\cdot {39\over 51}\cdot{26\over 50}\cdot{13\over 49}. $$

You have it.

Here is a second solution. There are ${52\choose 4}$ hands of size 4. Now pick the four cards of different suits; there are $13^4$ ways to do this.