Difference between revisions of "2002 AMC 12B Problems/Problem 11"
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Revision as of 16:25, 18 January 2008
Problem
The positive integers 
and 
are all prime numbers. The sum of these four primes is
Solution
Since 
and must have the same parity, and since there is only one even prime number, it follows that and are both odd. Thus one of 
is odd and the other even. Since 
, it follows that 
(as a prime greater than 
) is odd. Thus 
, and 
are consecutive odd primes. At least one of is divisible by 
, from which it follows that 
and 
. The sum of these numbers is thus 
, which is prime 
.
See also
| 2002 AMC 12B (Problems • Answer Key • Resources) | |
| Preceded by Problem 10 |
Followed by Problem 12 |
| 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 | |
