Difference between revisions of "2007 AMC 12B Problems/Problem 8"

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#REDIRECT [[2007 AMC 10B Problems/Problem 12]]
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==Problem==
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Tom's age is <math>T</math> years, which is also the sum of the ages of his three children. His age <math>N</math> years ago was twice the sum of their ages then. What is <math>T/N</math> ?
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<math>\mathrm {(A)} 2</math>  <math>\mathrm {(B)} 3</math>  <math>\mathrm {(C)} 4</math>  <math>\mathrm {(D)} 5</math>  <math>\mathrm {(E)} 6</math>
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==Solution==
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<math>T=a+b+c</math>
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<math>T-N=2(a-N+b-N+c-N)=2(a+b+c)-6N=2T-6N</math>
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<math>2T-6N=T-N</math>
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<math>T=5N</math>
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<math>T/N=5 \Rightarrow \mathrm {(D)}</math>
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==See Also==
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{{AMC12 box|year=2007|ab=B|num-b=7|num-a=9}}

Revision as of 14:41, 14 January 2016

Problem

Tom's age is $T$ years, which is also the sum of the ages of his three children. His age $N$ years ago was twice the sum of their ages then. What is $T/N$ ?

$\mathrm {(A)} 2$ $\mathrm {(B)} 3$ $\mathrm {(C)} 4$ $\mathrm {(D)} 5$ $\mathrm {(E)} 6$

Solution

$T=a+b+c$

$T-N=2(a-N+b-N+c-N)=2(a+b+c)-6N=2T-6N$

$2T-6N=T-N$

$T=5N$

$T/N=5 \Rightarrow \mathrm {(D)}$

See Also

2007 AMC 12B (ProblemsAnswer KeyResources)
Preceded by
Problem 7
Followed by
Problem 9
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AMC 12 Problems and Solutions