Series: Arithmetic Progression Formula Manipulation

Worked Solution:

The formula for the sum, S of n terms of the arithmetic series starting at a whose terms have a common difference of d is:

S =	n (2 a + (n – 1) d ) 2

For this arithmetic series, we have

a =

–  51 5

,

n =

27

and

d =

–  217 20

–

–  51 5

=

–  13 20

With the values for this series we have:

S =	27 ( 2× –  51 5 + ( 27 –1) –  13 20 ) 2

S =

–  10071 20

= –503.55