The sum of the sequence of 685+678+671+664+...+6

Mathematics

1 answer:

lukranit [14]3 years ago

3 0

Answer:

Sum of the sequence (Sn) = 33,859

Step-by-step explanation:

Given:

Sequence = 685+678+671+664+...+6

Find:

Sum of the sequence (Sn)

Computation:

a = 685

d = 678 - 985 = -7

an = 6

an = a+(n-1)d

6 = 685+(n-1)(-7)

-679 = (n-1)(-7)

97 = n-1

n = 98

So,

Sum of the sequence (Sn) = (n/2)[a+an]

Sum of the sequence (Sn) = (98/2)[685+6]

Sum of the sequence (Sn) = (49)(691)

Sum of the sequence (Sn) = 33,859

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