2002 AMC 10A Problem 16

Attempt Problem 16 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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16.

If a+1a+1 =b+2=b+2 =c+3=c+3 =d+4=d+4 =a+b+c+d+5,=a+b+c+d+5, then a+b+c+da+b+c+d is

5-5

103-\dfrac{10}{3}

73-\dfrac{7}{3}

53\dfrac{5}{3}

55

Answer: B
Concepts:system of equationssubstitution
Difficulty rating: 1330
Solution:

Let the common value be k.k. Then a=k1,a=k-1, b=k2,b=k-2, c=k3,c=k-3, d=k4,d=k-4, so a+b+c+d=4k10.a+b+c+d=4k-10.

Since a+b+c+d+5=k,a+b+c+d+5=k, we get 4k10+5=k,4k-10+5=k, so 3k=53k=5 and k=53.k=\dfrac{5}{3}. Then a+b+c+d=k5a+b+c+d=k-5 =535=103.=\dfrac{5}{3}-5=-\dfrac{10}{3}.

Thus, the correct answer is B.

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