A reality example of Probability
Poker cards
52 cards at a deck with 4 type hearts, club, diamonds, spades, and including 13 for each.
- What is the probability of choose 2 red cards from this deck
52 cards: $\frac{26}{52} \cdot \frac{25}{51}$
- What is the probability of choose number 4 cards from this deck
52 cards, 4 cards having number 4: $\frac{4}{52}$
- What is the probability of choosing number 4 cards from this deck? Given these are black cards
52 cards, 4 cards having number 4 with 2 blacks and 2 reds: $\frac{2}{52}$
Numeric numbers
How many number we can arrange 3 digits from 0-9 with:
No restrictions? 000,999: 1000
ABC: 10x10x10 =$10^3$ =1,000
What happen if different numbers:
ABC: 10x9x8 =720