Question

Check whether $25110$ is divisible by $45$

Answer 1

First we have to break $45$ into factors $5$ and $9$ and
Now, we have to check simultaneously both the conditions of divisibility by $5$ and $9$
$\left(i\right)$ for divisible by $5$, The last digit should either be $0$ or $5$
$\left(ii\right)$ for divisible by $9$, the sum of all digits must be divisible by $9$
So, as we can see $\left(i\right)$ is satisfying $25110$
and $2+5+1+1+0=9$ hence,$\left(ii\right)$ is also satisfying $25110$
Therefore $25110$ is divisible by $45$.