If `S_(5) = 15 and S_(6) = 21, "find "t_(6)`.

If for a G.P. { t_(n)}, S_(2) =15 and S_(4) =255, find a and r.

(i) Given a G.P. with a=729 and 7th term 64 find S_(7) . (ii) If {a_(n)} is a G.P. and a_(1)=4,r=5 , find a_(6) and S_(6) .

If for a G.P. { t_(n)},t_(2) =-6 and t_(5) =48 find S_(7) .

"If A" =[{:(p, q),(r, s):}] , ps = 15 and det A = 21, then find the value of qr. (a) 6 (b) -6 (c) 5 (d) -8

If for an A.P. (i) a=6, d=3, find S_(10) (ii) a=6, d=3 , find S_(6)

If for an A.P. (i) a=6, d=3, find S_(10) (ii) a=6, d=3 , find S_(6)

If for an A.P., t_(8) = 36 , find S_(15) .

If for an A.P., t_(8) = 36 , find S_(15) .

In a harmonic progression t_(1), t_(2), t_(3),……………., it is given that t_(5)=20 and t_(6)=50 . If S_(n) denotes the sum of first n terms of this, then the value of n for which S_(n) is maximum is

In a harmonic progression t_(1), t_(2), t_(3),……………., it is given that t_(5)=20 and t_(6)=50 . If S_(n) denotes the sum of first n terms of this, then the value of n for which S_(n) is maximum is