Initially, a standard deck of cards has 52 cards.
There are 13 cards of each suit: hearts, diamonds, clubs, and spades.
Hearts and diamonds are red, while clubs and spades are black.
So there are 26 red cards and 26 black cards.
We are given that 2 cards of hearts are missing and 4 cards of spades are missing.
The total number of missing cards is $2 + 4 = 6$.
The number of cards remaining is $52 - 6 = 46$.
Originally, there were 13 spades, but 4 are missing.
So the number of spades remaining is $13 - 4 = 9$.
Originally, there were 13 clubs, and no clubs are missing.
So the number of clubs is 13. The total number of black cards remaining is $9 + 13 = 22$.
The probability of getting a black card from the remaining pack is the number of black cards remaining divided by the total number of cards remaining: $$ P(\text{black card}) = \frac{\text{Number of black cards remaining}}{\text{Total number of cards remaining}} = \frac{22}{46}$$
Four students of class XII are given a problem to solve independently. Their respective chances of solving the problem are: \[ \frac{1}{2},\quad \frac{1}{3},\quad \frac{2}{3},\quad \frac{1}{5} \] Find the probability that at most one of them will solve the problem.
Two persons are competing for a position on the Managing Committee of an organisation. The probabilities that the first and the second person will be appointed are 0.5 and 0.6, respectively. Also, if the first person gets appointed, then the probability of introducing a waste treatment plant is 0.7, and the corresponding probability is 0.4 if the second person gets appointed.
Based on the above information, answer the following