Question

Suppose $x$ and $y$ are natural numbers, then the number of ordered pairs $(x,y)$ which satisfy $x+y\le 5$ is

• A. $25$
• B. $16$
• C. $9$
• D. $10$

Answer 1

The correct option is D $10$

$x,y$ are natural numbers
$x+y\le 5$
$x=1\Rightarrow y=1,2,3,4$
$x=2\Rightarrow y=1,2,3$
$x=3\Rightarrow y=1,2$
$x=4\Rightarrow y=1$
$\therefore$ no. of ordered pairs is $10$