MathDB

28

Part of 2009 National Olympiad First Round

Problems(1)

Divide Z into n subset no difference of two is prime

Source: 0

4/28/2009
We divide entire Z Z into n n subsets such that difference of any two elements in a subset will not be a prime number. n n is at least ?
<spanclass=′latex−bold′>(A)</span> 6<spanclass=′latex−bold′>(B)</span> 5<spanclass=′latex−bold′>(C)</span> 4<spanclass=′latex−bold′>(D)</span> 3<spanclass=′latex−bold′>(E)</span> None<span class='latex-bold'>(A)</span>\ 6 \qquad<span class='latex-bold'>(B)</span>\ 5 \qquad<span class='latex-bold'>(C)</span>\ 4 \qquad<span class='latex-bold'>(D)</span>\ 3 \qquad<span class='latex-bold'>(E)</span>\ \text{None}