Difference between revisions of "2004 AMC 10A Problems/Problem 7"

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Therefore, there are <math>5\times8+4\times7+3\times6+2\times5+1\times4=40+28+18+10+4=100</math> oranges in the stack <math>\Rightarrow\mathrm{(C)}</math>.
 
Therefore, there are <math>5\times8+4\times7+3\times6+2\times5+1\times4=40+28+18+10+4=100</math> oranges in the stack <math>\Rightarrow\mathrm{(C)}</math>.
  
==See Also==
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== See also ==
 
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{{AMC10 box|year=2004|ab=A|num-b=6|num-a=8}}
*[[2004 AMC 10A Problems]]
 
 
 
*[[2004 AMC 10A Problems/Problem 6|Previous Problem]]
 
 
 
*[[2004 AMC 10A Problems/Problem 8|Next Problem]]
 
  
 
[[Category:Introductory Algebra Problems]]
 
[[Category:Introductory Algebra Problems]]

Revision as of 02:39, 11 September 2007

Problem

A grocer stacks oranges in a pyramid-like stack whose rectangular base is 5 oranges by 8 oranges. Each orange above the first level rests in a pocket formed by four oranges below. The stack is completed by a single row of oranges. How many oranges are in the stack?

$\mathrm{(A) \ } 96 \qquad \mathrm{(B) \ } 98 \qquad \mathrm{(C) \ } 100 \qquad \mathrm{(D) \ } 101 \qquad \mathrm{(E) \ } 134$

Solution

There are $5\times8=40$ oranges on the 1st layer of the stack. When the 2nd layer is added on top of the first, it will be a layer of $4\times7=28$ oranges. When the third layer is added on top of the 2nd, it will be a layer of $3\times6=18$ oranges, etc.

Therefore, there are $5\times8+4\times7+3\times6+2\times5+1\times4=40+28+18+10+4=100$ oranges in the stack $\Rightarrow\mathrm{(C)}$.

See also

2004 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 6
Followed by
Problem 8
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 10 Problems and Solutions