Question

Using divisibility tests, determine $21084$ is divisible by $4$ and $8$.

Answer 1

If the last two digits of a whole number are divisible by $4$ , then the entire number is divisible by $4$
When $84÷4=21$, we get remainder zero, so $21084$ is divisible by $4$
If the last three digits of a whole number are divisible by $8$ , then the entire number is divisible by $8$
When $084$ is divided by $8$, we get remainder $4$, so $21084$ is not divisible by $8$
Hence $21084$ is divisible by $4$ but not divisible by $8$.