Question

the first term of an arithmetic sequence is 3000 and the tenth term is 1200. the sum of the first 20 terms of the sequence

Answer 1

Explanation:

B

1100

To find the sum of the first n terms of an arithmetic series use the formula,

S

n

=

2

n(a

1

+a

n

)

S

20

=

2

20(10+100)

S

20

=

2

2200

S

20

=1100