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Difference between revisions of "1985 AJHSME Problems/Problem 6"

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==Solution==
 
==Solution==
  
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===Solution 1===
 
We could solve the first equation for the thickness of one sheet of paper, and divide into the 2nd equation (which is one way to do the problem), but there are other ways, too.
 
We could solve the first equation for the thickness of one sheet of paper, and divide into the 2nd equation (which is one way to do the problem), but there are other ways, too.
  
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<math>750</math> is <math>\boxed{\text{D}}</math>
 
<math>750</math> is <math>\boxed{\text{D}}</math>
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===Solution 2===
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We can set up a direct proportion relating the amount of sheets to the thickness because according to the problem, all the papers have the same thickness.
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Our proportion is <cmath>\frac{5}{500}=\frac{7.5}{x}</cmath> where <math>x</math> is the number we are looking for.
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Next, we cross-multiply to get <math>5x=500 \times 7.5</math> so <math>x=750</math> which is <math>\boxed{\text{D}}</math>
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~GrantStar
  
 
==See Also==
 
==See Also==

Revision as of 15:14, 1 September 2019

Problem

A ream of paper containing $500$ sheets is $5$ cm thick. Approximately how many sheets of this type of paper would there be in a stack $7.5$ cm high?

$\text{(A)}\ 250 \qquad \text{(B)}\ 550 \qquad \text{(C)}\ 667 \qquad \text{(D)}\ 750 \qquad \text{(E)}\ 1250$

Solution

Solution 1

We could solve the first equation for the thickness of one sheet of paper, and divide into the 2nd equation (which is one way to do the problem), but there are other ways, too.

Let's say that $500\text{ sheets}=5\text{ cm}\Rightarrow \frac{500 \text{ sheets}}{5 \text{ cm}} = 1$. So by multiplying $7.5 \text{ cm}$ by this fraction, we SHOULD get the number of sheets in 7.5 cm. Solving gets

\begin{align*} \frac{7.5 \times 500}{5} &= 7.5 \times 100 \\ &= 750 \text{ sheets} \\ \end{align*}

$750$ is $\boxed{\text{D}}$

Solution 2

We can set up a direct proportion relating the amount of sheets to the thickness because according to the problem, all the papers have the same thickness. Our proportion is \[\frac{5}{500}=\frac{7.5}{x}\] where $x$ is the number we are looking for. Next, we cross-multiply to get $5x=500 \times 7.5$ so $x=750$ which is $\boxed{\text{D}}$

~GrantStar

See Also

1985 AJHSME (Problems • Answer Key • Resources)
Preceded by
Problem 5 		Followed by
Problem 7
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 AJHSME/AMC 8 Problems and Solutions


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