2002 AMC 10A Problem 2

Attempt Problem 2 of the 2002 AMC 10A 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 2002 AMC 10A solutions, or check the answer key.

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2.

For the nonzero numbers a,a, b,b, and c,c, define (a,b,c)=ab+bc+ca.(a,b,c)=\dfrac{a}{b}+\dfrac{b}{c}+\dfrac{c}{a}. Find (2,12,9).(2,12,9).

44

55

66

77

88

Answer: C
Concepts:custom operationfraction
Difficulty rating: 960
Solution:

(2,12,9)=212+129+92=16+43+92. \begin{aligned} (2,12,9) &= \dfrac{2}{12}+\dfrac{12}{9}+\dfrac{9}{2} \\ &= \dfrac{1}{6}+\dfrac{4}{3}+\dfrac{9}{2}. \end{aligned} Over a denominator of 6,6, this is 1+8+276=366=6.\dfrac{1+8+27}{6}=\dfrac{36}{6}=6.

Thus, the correct answer is C.

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