A geometric progression has first term 100 and sum to infinity 2000. Find the second term. [3]
Solution
The sum to infinity of a geometric progression is given by the formula:
\(S = \frac{a}{1-r}\)
where \(a\) is the first term and \(r\) is the common ratio.
Given \(a = 100\) and \(S = 2000\), we have:
\(\frac{100}{1-r} = 2000\)
Solving for \(r\):
\(100 = 2000(1-r)\)
\(100 = 2000 - 2000r\)
\(2000r = 2000 - 100\)
\(2000r = 1900\)
\(r = \frac{1900}{2000} = \frac{19}{20}\)
The second term of the progression is \(ar\):
\(ar = 100 \times \frac{19}{20} = 95\)
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