Question 1172363
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The ratio  {{{a[8]/a[1]}}}  is equal to  {{{640/5}}} = 128 = {{{2^7}}}.


From the other hand side, the ratio  {{{a[8]/a[1]}}}  is  {{{r^7}}}.


Therefore,  r = 2 (the common ratio).


Hence,  {{{a[10]}}} = {{{a[1]*r^9}}} = 5*512 = 2560.
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Solved. &nbsp;&nbsp;&nbsp;&nbsp;//  &nbsp;&nbsp;&nbsp;&nbsp;All questions are answered.