2009 AMC 12B Problem 12
Attempt Problem 12 of the 2009 AMC 12B below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2009 AMC 12B solutions, or check the answer key.
All problems are used with official legal permission of the Mathematical Association of America (MAA).
12.
The fifth and eighth terms of a geometric sequence of real numbers are and respectively. What is the first term?
Answer: E
Small hint:
The ratio of the eighth term to the fifth term is
Big hint:
so ; then divide by
Solution:
The eighth term divided by the fifth term is so
The fifth term is so
Thus, the correct answer is E.
Problem 12 in other years
- 1950 AMC 12
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