Find the sum of the first 13 terms of the A.P: `-6,\ 0,\ 6,\ 12 ,\ dot`

Find the sum of the first 11 terms of the A.P.: 2,\ 6,\ 10 ,\ 14 ,\ ddot

Find the sum of the first 10 terms of the A.P. 6,4,2,…..

Find the sum of the first 12 terms of the A.P. -37, -33, -29…….. .

The sum of first 16 terms of the A.P.: 10,6,2,... Is

The sum of first 16 terms of the A.P.: 10,6,2,… is :

Find the sum of first 100 terms of A.P. 14, 16, 18,……..

Find the sum of 10 terms of the G.P.3,6,12,dots

Find the number of terms of the A.P. -12 ,\ -9,\ -6,\ dot,\ 12 . If 1 is added to each term of this A.P., then find the sum of all terms of the A.P. thus obtained.

The sum of the first five terms of an A.P. and the sum of the first seven terms of the same A.P. is 167. If the sum of first 10 terms of this A.P. is 235, find the sum of its first twenty terms.

The first term of an A.P. is 5 and the common difference is 4. Complete the following activity and find the sum of first 12 terms of the A.P. Here, a=5, d=4,S_(12)=? S_(n)=(n)/(2)[.............] thereforeS_(12)=(12)/(2)[10+..........] =6xx...............=.............