Question

The number of two-digit numbers which are of the form $xy$ with $y<x$ are given by

• A. $60$
• B. $55$
• C. $50$
• D. $45$

Answer 1

Answer: (D)

$45$

When Zero is in the place of y then there are 9 numbers and when 1 is in place of y there are 8 numbers and so on. So required number is

$\sum _{n=1}^{9}n=45$