Problem
Each straight run of ribbon lies flat along a box edge, so it is exactly that edge's length.
A ribbon pressed flat along an edge can't be longer or shorter than that edge — recognizing the parallel edges is a 4th-grade geometry idea.
4.G.A.2Draw A DiagramThe first loop goes right around one face, covering two widths and two heights: 54 cm.
Going all the way around a rectangle uses two of each side length — the same as finding a perimeter.
4.MD.A.3Identify SubproblemsOne loop of ribbon is as long as the way round one face of the box.
The loop goes over the top, down one side, across the bottom and back up the other side, tracing the whole way round that face with nothing missed and nothing covered twice.
That way round takes each of the face's two edge lengths twice over, because the opposite sides of a face are the same length.
The second loop wraps the other face, covering two depths and two heights: 46 cm.
Turning the box and imagining the second loop, it is the same kind of trip around the rectangle on the other pair of faces.
4.MD.A.3Visualize Spatial RelationshipsAdd the ribbon used by the two loops to get the length that actually goes around the box.
The wrapping is just the two loops together, so add their lengths.
4.MD.A.2Identify SubproblemsFinally, add the 30 cm used for the bow (knot) on the top.
The bow is extra ribbon beyond the wrapping, so it joins the total.
4.MD.A.2Identify SubproblemsRibbon pressed flat along a box is as long as the edge it follows, so just add up the edges it covers — then add the bow.