Question 7
A strip is a grid-cell polygon whose cells can all be visited in a path using only upward or rightward steps between side-adjacent cells. Congruent copies can be fitted together by successive translations by$(-1,1)$. Prove that for every strip with an even number of cells there is an odd$k$ such that the union of$k$ successive translated copies can be cut along grid lines into two congruent parts. Congruence may include reflection or rotation.
