



 
Hi Glen, You know that the common ration r is 2.5 since 0.1024 × 2.5 = 0.256. Thus you know the third term is
and the fourth term is
etc. What I hope you see here is that each term is 0.1025 × 2.5^{power} where power is one less than the term number. So, for example the fifth term is 0.1025 × 2.5^{51} = 0.1025 × 2.5^{4}. Thus if the middle term is term number m then the middle term is 0.1025 × 2.5^{m1}. Hence
so
Evaluate the right side and then use logarithms to solve for m. I hope this helps,  


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