The first term of a geometric progression is 16 and the fourth term is \(\frac{27}{4}\). Find the sum to infinity of the progression.
Solution
Let the first term be \(a = 16\) and the common ratio be \(r\).
The fourth term is given by \(ar^3 = \frac{27}{4}\).
Substitute \(a = 16\) into the equation:
\(16r^3 = \frac{27}{4}\)
Divide both sides by 16:
\(r^3 = \frac{27}{64}\)
Take the cube root of both sides:
\(r = \frac{3}{4}\)
The sum to infinity of a geometric progression is given by:
\(S = \frac{a}{1 - r}\)
Substitute \(a = 16\) and \(r = \frac{3}{4}\):
\(S = \frac{16}{1 - \frac{3}{4}}\)
\(S = \frac{16}{\frac{1}{4}}\)
\(S = 16 \times 4 = 64\)
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