The formula for geometric sequences is $a = (a1 * r^{n-1})$, right?
Why isn't it working for this problem? $400, 320, 256\cdots$ What is the $6$th term?
$a_6 = 400\times{4/5}^5$?
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It should work. The answer is $\dfrac{16384}{125}$ isn't it? – Edward Jiang Jan 14 '15 at 01:40
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I'm getting 64/125? – John Jan 14 '15 at 01:42
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how are you getting that? – benji Jan 14 '15 at 01:45
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I'm putting those numbers into my calculator. I first tried it on my tablet's calculator, then I reached for my scientific one. Am I doing something wrong? – John Jan 14 '15 at 01:45
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I think you're doing $400\times\dfrac{4}{5^5}$ rather than $400\times\left(\dfrac{4}5\right)^4$. – Edward Jiang Jan 14 '15 at 01:49
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I rolled back my edit since it caused misinterpretation of the problem. – Edward Jiang Jan 14 '15 at 01:51