The first term of an arithmetic progression is 1 and the sum of the first nine terms equals 369. The first and the ninth term of a geometric progression with real common ratio coincide with the first

Question

The first term of an arithmetic progression is 1 and the sum of the first nine terms equals 369. The first and the ninth term of a geometric progression with real common ratio coincide with the first and the ninth term of the arithmetic progression. Find the seventh term of the geometric progression.

Answer:

27

Solution:

$369 = \frac{9}{2} [2 (1) + (9 - 1) d]$ , so $82 = 2 + 8 d$ and $d = 10$ .

TestHub · Accepted Answer

369 = 2 9 ​ [ 2 ( 1 ) + ( 9 − 1 ) d ] , so 82 = 2 + 8 d and d = 10 .

Mathematics - Sequence & Series Question with Solution | TestHub

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