Khairil has \(40\) cards consisting of white, blue and red. If a card is chosen at random, the probability of choosing a red card is \(\dfrac{3}{5}\). Calculate
a) number of cards in red.
b) the probability of choosing a blue card if Khairil has \(8\) white cards.
Solution:
If:
\(\begin{aligned}P &= \text{White card event selected.}\\ B &= \text{Blue card event selected.}\\ M &= \text{Red card event selected.}\\ S &= \text{Sample space}\end{aligned}\)
a)
\(\begin{aligned}n(S) &= 40\\ n(M)&=P(M)\times n(S)\\&=\dfrac{3}{5}\times40\\&=24.\end{aligned}\)
b)
\(\begin{aligned}\text{Give,} \\\,\\n(P) &= 8\\ n(B) &= 40 – 24 – 8 = 8\\\,\\ P(B)&=\dfrac{n(B)}{n(S)}\\&=\dfrac{8}{40}\\&=\dfrac{1}{5}. \end{aligned}\)
