# Math

the 8th terms of a geometry progression is 640. if the first term is 5, find the common ratio and the 10th terms?

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1. http://www.mathsisfun.com/algebra/sequences-sums-geometric.html

640 = 5r^7
128 = r^7
r = 128^(1/7) = 2 of course
so what is 5 * 2^9 ?

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