how to find number of terms

Find the sum to n terms of the series 1+4/5+7/5^2+10/5^3+…… find the sum to infinite number of terms.

The number of terms in an A.P.is even; the sum of the odd terms is 24, of the even terms 30, and the last term exceeds the first by 10 find the number of terms

First term of an A,P is -5 and its last term is 45 If the sum of these terms is 120 find the number of terms.

The first term of an AP is -5 and the last term is 45. If the sum of the terms of the AP is 120, then find the number of terms and the common difference.

The number of terms in an A.P. is even , the sum of odd terms is 63 and that of even terms is 72 and the last term exceeds the first term by 16.5 . Find the number of terms :

Number of terms of an AP is even.The sum of odd terms is 24 an that of even terms is 30 . The last term exceeds the first term by 10(1)/(2) . Find the number of terms.

The first term of an A.P is 7 , the last term is 47 and the sum is 432 . Find the number of terms and the common difference .

The first term of an AP.Is,the common difference is 3 and the last term is 80; find the number of terms.

The first term of an A.P. is 5, the common difference is 3 and the last term is 80; find the number of terms.