[" 15.The "14" th term of an "A" ."P" ,is twice its "8" th term.If the "6" th term is "-8" ,then find the sum o "],[" its first "20" terms."(3)]

The 14 th term of an A.P.is twice its 8 th term. If its 6th term is - 8 ,then find the sum of its first 20 terms.

The 14th term of an A.P. is twice its 8th term. If its 6th term is -8, then find the sum of its first 20 terms.

The 29^(th) term of an A.P is twice its 19^(th) term. Its 9^(th) term is equal to

The first term of G.P. is 27 and 8th term is 1/81 . Find the sum of its first 10 terms.

The 17 th term of an A.P.is 5 more than twice its 8 th term.If the 11 th term of the A.P.is 43, is 43, find the n^(th) term.

The 17th term of an A.P. is 5 more than twice its 8th term. If the 11th term of the A.P. is 43, find the n^(t h) term.

The 6 th term of an AP is 20 and its 11 th term is 35. Find the 25 th term of the AP.

The first term of a GP is 27 and its 8th terms is 1/81 . Find the sum of its first 10 terms.

If the sum of first 8 terms of an Arithmetic progression is 136 and that of first 15 terms is 465, then find the sum of first 25 terms. OR Ths sum of the 5th and 9th terms of an A.P. is 40 and the sum of the 8th and 14th term is 64. Find the sum of the first 20 terms.