If $2x, x + 8, 3x + 1$ are in $A.P.$,then the value of $x$ will be

If the sum of the series $54 + 51 + 48 + \dots$ is $513$,then the number of terms is:

If $\frac{1}{p + q}, \frac{1}{r + p}, \frac{1}{q + r}$ are in $A.P.$,then

The number of terms in an $A.P.$ is even. The sum of the odd terms is $24$ and the sum of the even terms is $30$. If the last term exceeds the first term by $10\frac{1}{2}$,then the number of terms in the $A.P.$ is:

If $< a_n >$ is an $A.P.$ and $a_1 + a_4 + a_7 + \dots + a_{16} = 147$,then $a_1 + a_6 + a_{11} + a_{16}$ is equal to

The sum of the numbers between $100$ and $1000$ which are divisible by $9$ is: