Ten > Sequence and Series

Asked by Basanta · 2 years ago

The first and last term of an arithmetic series having some terms are 4 and 40 respectively. The sum of all terms is 220.

1. Write the formula to calculate the the sum of the first n terms of the series.
2. Find the total number of terms in the series.
3. What should be added to the third term of the series so that the first three terms form a geometric series? Find it.