Question

The first and last terms of a 10-term arithmetic series are listed in the table. What is the sum of the series?

Term Number Term
1 3
10 75

Answer 1

The sum of an arithmetic series:

`S_n=(n(a_1+a_n))/(2)`


`a_1=3 \\ a_(10)=75 \\ \\ S_(10)=(10(a_1+a_(10)))/(2)=(10(3+75))/(2)=5(3+75)=5 * 78=390`

The sum of the series is 390.