Question

8 th term of an arithmetic sequence is 20 What is the sum of its first 15 terms ?
with equation
please fast​

Answer 1

Answer:

A very interesting property of AP is that the middle term is the arithmetic mean of the series if number of terms is odd.

In our series, number of terms is 15 and 8th term is the middle term.

=> The arithmetic mean of the series is the 8th term = 20

=> Sum of 15 terms = 20 x 15 = 300.

Answer 2

Answer:

=> Sum of 15 terms = 20 x 15 = 300

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