2008 AMC 10A Problem 5

Attempt Problem 5 of the 2008 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 2008 AMC 10A solutions, or check the answer key.

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5.

Which of the following is equal to the product

8412816124n+44n20082004? \begin{aligned} &\dfrac{8}{4} \cdot \dfrac{12}{8} \cdot \dfrac{16}{12} \cdots \dfrac{4n+4}{4n} \\ &\quad \cdots \dfrac{2008}{2004}? \end{aligned}

251251

502502

10041004

20082008

40164016

Answer: B
Concepts:telescopingfraction
Difficulty rating: 1050
Solution:

Every denominator except the first cancels with the numerator of the previous fraction, so the whole product telescopes to 20084=502.\dfrac{2008}{4} = 502.

Thus, the correct answer is B.

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