The probability of getting head and tail alternately in three throws of a coin (or a throw of three coins) is:

From $10,000$ lottery tickets numbered from $1$ to $10,000$,one ticket is drawn at random. What is the probability that the number marked on the drawn ticket is divisible by $20$?

In a box,there are $2$ red,$3$ black,and $4$ white balls. If three balls are drawn together,what is the probability that they are of the same color?

The probability that a contractor will get a plumbing contract is $2/3$ and the probability that he will not get an electric contract is $5/9$. If the probability of getting at least $1$ contract is $4/5$,what is the probability that he will get both?

Study the given information carefully and answer the questions that follow: $A$ basket contains $4$ red,$5$ blue and $3$ green marbles. If $3$ marbles are picked at random,what is the probability that either all are green or all are red?

When two dice are thrown simultaneously,what is the probability that the sum of numbers appeared is an odd number?