The sum of some terms of a G.P. is 315 whose first term and the common ratio are 5 and 2, respectively. Find the last term and the number of terms.

Explanation

Let there be n terms in the G.P. with first term `a=5` and common ratio `r=2`. Then,


Sum of n terms `= 315`


`(a(r^n−1)​)/(r-1)=315`


`(5(2^n−1​))/(2-1)=315`


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