A bag contains $5$ red marbles and $3$ blue marbles. If one marble is drawn at random, what is the probability that it is **red**?
A$\dfrac{3}{8}$
B$\dfrac{5}{8}$
C$\dfrac{3}{5}$
D$\dfrac{5}{3}$
Answer & Solution
Correct answer: B. $\dfrac{5}{8}$
Total marbles $= 5 + 3 = 8$. Favourable (red) $= 5$.
$P(\text{red}) = \dfrac{5}{8}$.
- Trap A returns the blue probability.
- Trap C uses the wrong denominator.
- Trap D inverts numerator and denominator — not a valid probability (must be $\le 1$).
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