Question

find the sum of the 9 terms of the series 7,14,21,..

Answer 1

Answer:

We need to start by finding the number of terms,

n

.

The formula

t

n

=

a

+

(

n

−

1

)

d

gives the nth term of an arithmetic series.

98

=

7

+

(

n

−

1

)

7

98

=

7

+

7

n

−

7

7

n

=

98

n

=

14

We can now apply the formula

s

n

=

n

2

(

t

1

+

t

n

)

to determine the sum of the series.

s

14

=

14

2

(

7

+

98

)

s

14

=

7

(

105

)

s

14

=

735

Step-by-step explanation:

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