# SOLUTION: I need to find the sum of the first n terms of the g.p. 4,12,36... and find the least value of n for which the sum is greater than 500,000. I know that r = 3 and a = 4 but then

Algebra ->  -> SOLUTION: I need to find the sum of the first n terms of the g.p. 4,12,36... and find the least value of n for which the sum is greater than 500,000. I know that r = 3 and a = 4 but then       Log On

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 Question 328501: I need to find the sum of the first n terms of the g.p. 4,12,36... and find the least value of n for which the sum is greater than 500,000. I know that r = 3 and a = 4 but then I am stuck.Answer by josmiceli(10616)   (Show Source): You can put this solution on YOUR website!the formula is: I'll find out when the sum is greater than 500000 Multiply both sides by I can take the log of both sides If , the left side is close to , so Putting this back into formula, The next whole number for is I think that would put over seems to be too small