Problem
The cross folds into a floor plus four walls, so the box has 5 faces and an open top.
Counting faces on a net is just matching each square of the cut-out to one face of the folded box — the center is the floor, the arms are the walls.
6.G.A.4Visualize Spatial RelationshipsTipped onto one bottom edge, the water pools there as a wedge with a flat, slanted top.
Tilt any cup of water and the water slides to the low side while its surface stays flat — that is the slanted plane you see.
6.G.A.4Visualize Spatial RelationshipsThe wedge lies on the floor and against the two walls meeting at that low edge: 3 of the 5 faces.
Pour water into a tilted open box: the floor is fully covered, the two near walls get wet up to the slanted line, and the far walls stay dry.
6.G.A.4Create A Physical RepresentationThe floor is wet all over, and each near wall is wet in a triangle standing on the fold edge.
A slanted flat water surface cuts each wall along a straight line, leaving a triangle of wet wall below it.
6.G.A.4Draw A DiagramUnfolded, shade the centre square whole and one triangle on each of the two neighbouring flaps.
Whatever touches across a fold edge in the box must touch across that same edge on the net — the colors line up when you fold it back.
6.G.A.4Draw A DiagramUnfolding the box lays each wet region onto its own square of the net without changing its shape.
Unfolding is simply folding run backwards, and neither one stretches or tears the surface, so every region keeps its shape and its size.
Each face of the box is one square of the net, so a wet patch on a face becomes a patch on exactly that square and on no other.
Water always slides to the lowest corner: it covers the floor and wets the two walls that meet there — so on the unfolded net you color the bottom plus two triangles.