The sum of $1 + 3 + 5 + 7 + \dots$ up to $n$ terms is:

Sum of the series $1 \cdot 2015 + 2 \cdot 2014 + 3 \cdot 2013 + \dots + 2015 \cdot 1$ is equal to :-

The sum of the $3^{rd}$ and the $4^{th}$ terms of a $G.P.$ is $60$ and the product of its first three terms is $1000$. If the first term of this $G.P.$ is positive,then its $7^{th}$ term is

$A$ ball rolling up an incline covers $36\, m$ during the first second,$32\, m$ during the second,$28\, m$ during the next and so on. How much distance will it travel during the $8^{th}$ second? (in $m$)

The first term of a harmonic progression is $1/7$ and the second term is $1/9$. The $12^{th}$ term is

For what value of $x,$ the numbers $-\frac{2}{7}, x, -\frac{7}{2}$ are in $G.P.$?