Difference between revisions of "2007 iTest Problems/Problem 1"
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<math>(2,2+2)\equiv (2,4)</math>. <math>4</math> isn't a prime, so this isn't a set of twin primes. | <math>(2,2+2)\equiv (2,4)</math>. <math>4</math> isn't a prime, so this isn't a set of twin primes. | ||
| − | <math>(3,3+2)\equiv (3,5)</math>. <math>5</math> is a prime, so the answer is <math>\frac{3+5}{2}=4\Rightarrow \boxed{A}</math>. | + | <math>(3,3+2)\equiv (3,5)</math>. <math>5</math> is a prime, so the answer is <math>\frac{3+5}{2}=4\Rightarrow \boxed{\mathrm{A}}</math>. |
===Alternate Solution=== | ===Alternate Solution=== | ||
| − | Seeing as <math>A</math> is the only choice, we determine that the answer is <math>\boxed{A}</math>. | + | Seeing as <math>A</math> is the only choice, we determine that the answer is <math>\boxed{\mathrm{A}}</math>. |
{{iTest box|before=First question|num-a=2|year=2007}} | {{iTest box|before=First question|num-a=2|year=2007}} | ||
[[Category:Introductory Number Theory Problems]] | [[Category:Introductory Number Theory Problems]] | ||
Revision as of 14:17, 11 December 2007
Problem
A twin prime pair is a set of two primes 
such that 
is 
greater than 
. What is the arithmetic mean of the two primes in the smallest twin prime pair?
Solution
We consider the first few primes.
. 
isn't a prime, so this isn't a set of twin primes.
. 
is a prime, so the answer is 
.
Alternate Solution
Seeing as 
is the only choice, we determine that the answer is 
.
| 2007 iTest (Problems, Answer Key) | ||
| Preceded by: First question |
Followed by: Problem 2 | |
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