The sum to infinity of a geometric progression is (-frac{1}{10}) and the first term is (-frac{1}{8}). Find the common ratio of the progression.
-
A.
(-frac{1}{5}) -
B.
(-frac{1}{4}) -
C.
(-frac{1}{3}) -
D.
(-frac{1}{2})
Correct Answer: Option B
Explanation
Sr = (frac{a}{1 – r})
(-frac{1}{10}) = (frac{1}{8} times frac{1}{1 – r})
(-frac{1}{10}) = (frac{1}{8(1 – r)})
(-frac{1}{10}) = (frac{1}{8 – 8r})
cross multiply…
-1(8 – 8r) = -10
-8 + 8r = -10
8r = -2
r = -1/4
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