7. A square of paper is cut into two pieces by a single straight cut. Which of the following shapes cannot be the shape of either piece?
A An isosceles triangle
B A right-angled triangle
C A pentagon
D A rectangle
E A square
Solution
E

Assuming one of the options cannot be formed, we answer the question by eliminating four of the options. The diagrams below show examples of how a square could be cut to form the first four shapes, with a dotted line representing the position of the cut.
Hence we conclude that the shape which cannot be obtained is a square.