How the 2D to 3D section works
Each item shows a flat pattern, the shape you would cut out of card, next to a drawing of the solid it folds into. Labels on one drawing have to be matched to labels on the other: prep material shows numbers on one and letters on the other, and you work out which go together once the pattern is folded. A marked face, such as one with an X, ties the two drawings together.
There is no scratch paper, as prep sites report it, so all the folding happens in your head.
How to solve a folding item
Work outwards from one face you are sure of:
- Find the marked face on both drawings. It fixes which way the pattern sits on the solid.
- Take the faces joined to it one at a time. Each dotted fold line on the pattern is an edge the two faces share on the solid.
- For a free edge on the pattern, ask which face it will meet when everything is folded. That meeting line is its edge on the solid.
- Expect two numbered edges to share one letter when they close up against each other in a seam.
- Remember the solid shows more letters than there are numbers, so some letters are not used.
Worked example
The pattern is a cross of six squares seen from outside. The middle square has an X and becomes the top of a cube. The squares above, left and right of it become the back, left and right faces; the square below it becomes the front, and one more square below that becomes the bottom.
The cube is drawn from the front right, above, showing the top, front and right faces. Its edges are lettered: C is top and front, E is top and right, A is the upright edge where front meets right, B is front and bottom, and G is right and bottom.
Edge 1, the fold between the X square and the front square, is C. Edge 2, the fold between the X square and the right square, is E. Edge 3, the right square’s free edge nearest the front square, folds down to meet the front face, so it is A. Edge 4, the front square’s free right edge, meets it there, so it is also A. Edge 5, the bottom square’s free right edge, meets the right face along the bottom, so it is G. The answers are C, E, A, A and G.
Tips for the real 2D to 3D section
- Start every item from the marked face. Guessing at an edge without a fixed face is where most errors come from.
- Fold real paper nets at home: cubes, wedges and pyramids. Seeing a seam close once makes it easier to picture.
- Keep an eye on the clock and move on from an item that will not resolve.
- Read the on-screen instructions on wrong answers before you start, so you know whether to guess.
- Practise on a computer screen rather than a phone, so the drawings are close to test-day size.
Practise 2D to 3D on CogniPrep
Our 2D to 3D game gives you 6 drawings in 15 minutes, each with five numbered pattern edges to match to the lettered edges of a solid, an X on the same face in both drawings, and letters that can be used twice. You can change answers on the current drawing, but moving on is final. Each wrong answer takes off a fraction of a mark and a blank scores nothing, so a blind guess gains nothing on average; your score out of 100 is your net marks over the 30 available. The count, clock and deduction are ours, because TSA publishes none.