Reasoning · Grade 4-1 Transformations of Figures
Problem
Only the near half shows; the far half is hidden.
This is the same fold-and-match idea as a line of symmetry: whichever half you keep, the mirror line makes the other half an exact copy of it, so the finished picture always folds onto itself along that diagonal.
4.G.A.3Visualize Spatial RelationshipsPair the triangles that face each other across the line.
Naming the three pairs in advance turns the drawing job into three small copying jobs, so no triangle can be forgotten or done twice.
4.G.A.3Make A Systematic ListFrom (1), copy the three near triangles unchanged.
The half nearest the viewer is not changed by the mirror at all, so it can simply be traced over from the original picture.
4.G.A.1Draw A DiagramFlipping them across the line gives the answer for (1).
Every corner of a shaded piece keeps its distance from the mirror line, so a midpoint of one diagonal has to land on a midpoint of the diagonal facing it — that is enough to place each copied piece exactly.
4.G.A.3Draw A DiagramEvery corner of a shaded piece keeps its distance from the mirror line, which is enough to place each copied piece exactly.
The mirror sends each point straight across the line to a point exactly as far away on the other side.
Each triangle on the near side has exactly one partner facing it, so copying is three small jobs and no piece is done twice.
From (2) the near half is the other three triangles.
Swapping viewpoints does not change the paper — only which half of it the mirror is willing to show you twice.
4.G.A.1Draw A DiagramFlipping those across gives the answer for (2).
A dot is the easiest case of all: it just moves straight across the mirror line to the point the same distance away, which lands it at the middle of the facing triangle.
4.G.A.3Draw A DiagramBoth pictures come out symmetric about the mirror.
Checking for a line of symmetry is a Grade 4 skill, and here it is not just a check but the definition of a correct answer.
4.G.A.3Create A Physical RepresentationA mirror never shows you the far half — it shows the near half twice, so the picture you see always folds onto itself along the mirror line.