Find the sum of all multiples of $9$ lying between $300$ and $700$.

Are the following pattern of the numbers in arithmetic progression (A.P.)?

$1, 5, 9, 13, 17, ...$

Check whether the following pattern of the numbers are in arithmetic progession (A.P.) or not.

$2, 6, 10, 16, 24, ...$

Is the pattern of numbers: $p, p+90, p+180, p+270, ...$ where $p={\left(999\right)}^{999}$, in arithmetic progression (A.P.)?