Question:
A pack of cards has one card missing. Two cards are drawn randomly and are found to be spades. The probability that the missing card is not a spade, is :
Correct Option: , 3
Solution:
$\mathrm{E}_{1}$ : Event denotes spade is missing
$\mathrm{P}\left(\mathrm{E}_{1}\right)=\frac{1}{4} ; \mathrm{P}\left(\overline{\mathrm{E}}_{1}\right)=\frac{3}{4}$
A : Event drawn two cards are spade
$P(A)=\frac{\frac{1}{4} \times\left(\frac{{ }^{12} C_{2}}{{ }^{51} C_{2}}\right)+\frac{3}{4} \times\left(\frac{{ }^{13} C_{2}}{{ }^{51} C_{2}}\right)+\frac{3}{4} \times\left(\frac{{ }^{13} C_{2}}{{ }^{51} C_{2}}\right)}{\frac{1}{4} \times\left(\frac{{ }^{12} C_{2}}{{ }^{51} C_{2}}\right)+\frac{3}{4} \times\left(\frac{{ }^{13} C_{2}}{{ }^{51} C_{2}}\right)}$
$=\frac{39}{50}$