Question

Let $a_1,a_2,a_3$, ..., an, be in A. P. and $S_n$ denotes the sum of first $n$ terms of this A. P. is $S_{10}$ =$390, \frac{a_{10}}{a_{50}} =\frac{15}{7}$, then $S_{15} -S_5 =$ _________.

Answer 1

The Correct Answer is: $365$