Complete Concept Guide (100% Curriculum Coverage)
1. Theoretical Probability Formula
For equally likely outcomes, the probability of event $E$ is: $$\mathbf{P(E) = \frac{\text{Number of outcomes favorable to } E}{\text{Total number of possible outcomes in sample space } S}}$$
• Range: $0 \le P(E) \le 1$.
• Complementary Rule: $\mathbf{P(E) + P(\bar{E}) = 1}$ (Probability of happening + not happening is strictly $1$).
2. The Standard 52-Card Deck Breakdown
Total: 52 cards split into 4 suits of 13 cards each:
• Red (26): Hearts (13), Diamonds (13).
• Black (26): Spades (13), Clubs (13).
• Face Cards (12): 4 Kings, 4 Queens, 4 Jacks.
• Aces (4): 1 in each suit (not considered face cards!).
3. Rolling Two Dice ($n = 36$)
When rolling two standard dice, there are $6 \times 6 = 36$ total outcomes: $(1, 1), (1, 2)\dots(6, 6)$. Sums range from $2$ (only $(1, 1)$) to $12$ (only $(6, 6)$).
Check Your Understanding (Diagnostic Practice Questions)
Diagnostic questions testing core conceptual clarity. Answers are hidden initially — solve each problem first, then click to reveal the step-by-step verified solution.
1
One card is drawn from a well-shuffled deck of 52 cards. Find the probability of getting: (a) A king of red color (b) A face card.
Reveal Answer & Explanation
Answer: (a) There are 2 red kings (hearts and diamonds) $\implies P = \frac{2}{52} = \frac{1}{26}$. (b) There are 12 face cards $\implies P = \frac{12}{52} = \frac{3}{13}$.
(a) 1/26 (b) 3/13.
2
If $P(E) = 0.05$, what is the probability of 'not $E$'?
Reveal Answer & Explanation
Answer: $P(\bar{E}) = 1 - P(E) = 1 - 0.05 = 0.95$.
0.95.
3
Two dice are thrown simultaneously. What is the probability of getting a doublet (same number on both dice)?
Reveal Answer & Explanation
Answer: Favorable doublets: $(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6)$ (6 outcomes). Total outcomes $= 36$. $P = \frac{6}{36} = \frac{1}{6}$.
1/6.
4
A bag contains 3 red balls and 5 black balls. A ball is drawn at random. What is the probability that it is not red?
Reveal Answer & Explanation
Answer: Total balls $= 8$. Favorable (black) $= 5$. $P(\text{not red}) = \frac{5}{8}$.
5/8.
5
Can the probability of an event be $-\frac{1}{5}$ or $1.2$? Explain.
Reveal Answer & Explanation
Answer: No, because the probability of any event is strictly bounded between $0$ and $1$ inclusive ($0 \le P(E) \le 1$). Probabilities can never be negative or exceed 1.
Probability must be between 0 and 1.
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