Dear Sir,

I have some

Difficulty in understanding the last part of the below problem and would be very grateful if you can show me how to do it.

Thank you very much

Best Regards

Kingman

A geometric progression has first term a (where a>0), and common ratio r.

The sum of the first n terms is Sn and the sum to infinity is S. Given that S2 is twice the value of the fifth term, find the value of r (no problem up till here. and r is found to be - 0.648)

Hence find the least value of n such that Sn is within 5% of S.

Can you provide the geometrical significance and interpretation of the last question?