Difference between revisions of "2007 AMC 8 Problems/Problem 19"

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== Solution ==
 
== Solution ==
  
Let the smaller of the two numbers be <math>x</math>. Then, the problem states that <math> (x+1)+x<100</math>. <math> (x+1)^2-x^2=x^2+2x+1-x^2=2x+1 </math>. <math> 2x+1 </math> is obviously odd, so only answer choices C and E need to be considered.
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Let the smaller of the two numbers be x Then, the problem states that (x+1)+x<100. (x+1)^2-x^2=x^2+2x+1-x^2=2x+1 2x+1 is obviously odd, so only answer choices C and E need to be considered.
  
<math> 2x+1=131 </math> refutes the fact that <math> 2x+1<100 </math>, so the answer is <math> \boxed{\mathrm{(C)} 79} </math>
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2x+1=131 refutes the fact that 2x+1<100 so the answer is C
  
 
==Video Solution by WhyMath==
 
==Video Solution by WhyMath==

Revision as of 18:36, 1 August 2021

Problem

Pick two consecutive positive integers whose sum is less than $100$. Square both of those integers and then find the difference of the squares. Which of the following could be the difference?

$\mathrm{(A)}\ 2 \qquad \mathrm{(B)}\ 64 \qquad \mathrm{(C)}\ 79 \qquad \mathrm{(D)}\ 96 \qquad \mathrm{(E)}\ 131$

Solution

Let the smaller of the two numbers be x Then, the problem states that (x+1)+x<100. (x+1)^2-x^2=x^2+2x+1-x^2=2x+1 2x+1 is obviously odd, so only answer choices C and E need to be considered.

2x+1=131 refutes the fact that  2x+1<100  so the answer is C

Video Solution by WhyMath

https://youtu.be/BrEqmDq82rw

~savannahsolver

See Also

2007 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
Problem 18
Followed by
Problem 20
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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