Question

A shopkeeper has 10 copies of each of nine different books, then number of ways in which atleast one book can be selected is-

• A. 9¹¹–1
• B. 10¹⁰–1
• C. 11⁹–1
• D. 10⁹

Answer 1

Answer: (C)

11⁹–1

Answer 2

$\underset{10}{\overset{B_{1}}{︸}}$ $\underset{10}{\overset{B_{2}}{︸}}$ $\underset{10}{\overset{B_{3}}{︸}}$……….$\underset{10}{\overset{B_{9}}{︸}}$

Selection of atleast one book $\underset{9times}{\overset{(10 + 1)(10 + 1)......(10 + 1)}{︸}}$– 1

= 11⁹ –1