If first 15th term of an A.P. is a, second term is b and nth term is 2 a, then sum of the n terms is :
A. \(\frac {ab}{2(b – a)}\)
B. \(\frac {2ab}{3(b – a)}\)
C. \(\frac {3ab}{2(b – a)}\)
D. \(\frac {3ab}{(b – a)}\)
Answer:C
If first 15th term of an A.P. is a, second term is b and nth term is 2 a, then sum of the n terms is :
A. \(\frac {ab}{2(b – a)}\) B. \(\frac {2ab}{3(b – a)}\) C. \(\frac {3ab}{2(b – a)}\) D. \(\frac {3ab}{(b – a)}\)