

InterviewSolution
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A card is drawn at random from a pack of 52 cards. Find the probability that the card drawn is (i) a black king (ii) either a black card or a king(iii) black and a king (iv) a jack, queen or a king (v) neither an ace nor a king (vi) spade or an ace (vii) neither an ace nor a king (viii) a diamond card (ix) not a diamond card (x) a black card (xi) not an ace (xii) not a black card |
Answer» Given: pack of 52 cards Formula: P(E) = \(\frac{favourable\,outcomes}{total\,possible\,outcomes}\) since a card is drawn from a pack of 52 cards, therefore number of elementary events in the sample space is n(S)= 52C1 = 52 (i) let E be the event of drawing a black king n(E)=2C1 =2 (there are two black kings one of spade and other of club) P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{2}{52}\) = \(\frac{1}{26}\) (ii) let E be the event of drawing a black card or a king n(E) = 26C1+4C1- 2C1= 28 we are subtracting 2 from total because there are two black king which are already counted and to avoid the error of considering it twice P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{28}{52}\) = \(\frac{7}{13}\) (iii) let E be the event of drawing a black card and a king n(E)=2C1 =2 (there are two black kings one of spade and other of club) P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{5}{52}\) = \(\frac{1}{26}\) (iv) let E be the event of drawing a jack, queen or king n(E)=4C1+ 4C1+ 4C1 = 12 P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{12}{52}\) = \(\frac{3}{13}\) (v) let E be the event of drawing neither a heart nor a king now consider E’ as the event that either a heart or king appears n(E’) = 6C1+ 4C1 - 1 = 16 (there is a heart king so it is deducted) P(E') = \(\frac{n(E')}{n(S)} \) P(E') = \(\frac{16}{52}\) = \(\frac{4}{13}\) P(E) = 1- P(E’) P(E) = 1 - \(\frac{4}{13}\) = \(\frac{9}{13}\) (vi) let E be the event of drawing a spade or king n(E)= 13C1 + 4C1 - 1 = 16 P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{16}{52}\) = \(\frac{4}{13}\) (vii) let E be the event of drawing neither an ace nor a king now consider E’ as the event that either an ace or king appears n(E’) = 4C1+ 4C1 = 8 P(E') = \(\frac{n(E')}{n(S)} \) P(E') = \(\frac{8}{52}\) = \(\frac{2}{13}\) P(E) = 1- P(E’) P(E) = 1 - \(\frac{2}{13}\) = \(\frac{11}{13}\) (viii) let E be the event of drawing a diamond card n(E)= 13C1 = 13 P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{13}{52}\) = \(\frac{1}{13}\) (ix) let E be the event of drawing not a diamond card now consider E’ as the event that diamond card appears n(E’) = 13C1 =13 P(E') = \(\frac{n(E')}{n(S)} \) P(E') = \(\frac{13}{52}\) = \(\frac{1}{4}\) P(E) = 1- P(E’) P(E) = 1 - \(\frac{1}{4}\) = \(\frac{3}{4}\) (x) let E be the event of drawing a black card n(E)= 26C1= 26 (spades and clubs) P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{26}{52}\) = \(\frac{1}{2}\) (xi) let E be the event of drawing not an ace now consider E’ as the event that ace card appears n(E’) = 4C1= 4 P(E') = \(\frac{n(E')}{n(S)} \) P(E') = \(\frac{4}{52}\) = \(\frac{1}{13}\) P(E) = 1- P(E’) P(E) = 1 - \(\frac{1}{13}\) = \(\frac{12}{13}\) (xii) let E be the event of not drawing a black card n(E) = 26C1= 26 (red cards of hearts and diamonds) P(E) = \(\frac{n(E)}{n(S)} \) P(E) = \(\frac{26}{52}\) = \(\frac{1}{2}\) |
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