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# Help

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An infinite geometric series has common ratio 1/8 and sum 60. What is the first term of the series?

Jan 5, 2021
edited by hihihi  Jan 5, 2021

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Let the first term be a. Because the sum of the series is 60, we have

$$60= \frac{a}{1-(1/8)} = \frac{a}{7/8} = \frac{8a}{7}.$$

Therefore, $$a=\frac{7}{8}\cdot60=\boxed{\frac{105}{2}}$$.

Jan 5, 2021

#1
+312
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$$60= \frac{a}{1-(1/8)} = \frac{a}{7/8} = \frac{8a}{7}.$$
Therefore, $$a=\frac{7}{8}\cdot60=\boxed{\frac{105}{2}}$$.