Question 1135959: For the series 16, 24, 36, 54,... find S7.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39618)   (Show Source):
Answer by MathTherapy(10552)  (Show Source):
You can put this solution on YOUR website! For the series 16, 24, 36, 54,... find S7.
That person is WRONG, as usual! This is NOT an A.P. with 4 as the common difference. It is in fact a G.P. with r or the common ratio being 1.5.
You can use the formula for a specific term in a G.P. to find the last term, or ( ), where: r is 1.5, and a1, or 1st term is 16.
Last term: 
Sum of a G.P.:  , where: n = 7 ; a1, or 1st term = 16 ; an, or LAST term = 182.25 ; r = 1.5
Sum of the 1st 7 terms of this G.P.: 
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