Question

A bag contains $10$ tickets numbered $1$ to $10$. Tickets are drawn one by one without replacement. The probability that the ticket number $7$ is drawn at $4$th draw is

• A. $\frac{1}{10}$
• B. $\frac{1}{{10}^4}$
• C. $\frac{1}{40}$
• D. $\frac{2}{5}$

Answer 1

The correct option is A $\frac{1}{10}$

To have ticket numbered $7$ at $4th$ draw ,

$\therefore$ Probability $=\frac{9}{10}\times \frac{8}{9}\times \frac{7}{8}\times \frac{1}{7}=\frac{1}{10}$

(On first draw,all tickets except $7$ is acceptable , likewise for two other draws).