Reasoning · Grade 2-1 Making Shapes

Problem

Divide a shape with straight cuts

On a square sheet, two straight cuts are drawn and the names and counts of the pieces recorded. The two diagonals give 4 triangles, and one other example gives 2 triangles, 1 quadrilateral and 1 hexagon. Find further ways that differ from these two.
4 triangles 2 triangles 1 quadrilateral 1 hexagon
Your answer
How to solve
Strategy Make a Systematic List — This is a 'how many different ways' enumeration, so I make a systematic list of the cut patterns, organized by what each cut connects to (corner-to-corner, side-to-opposite-side, side-to-adjacent-side) and whether the two cuts cross inside the square. I sketch each candidate (Draw a Diagram) and count each piece's sides. Thinking first about what ONE cut alone does (Solve an Easier Related Problem) makes the two-cut cases easy to predict.
1STEP 1

What one straight cut does

One cut splits the square into two pieces, and there are three ways to draw it.

1 cut → 2 pieces
2STEP 2

Way A: two parallel cuts (3 quadrilaterals)

Two parallel cuts make three strips: 3 quadrilaterals.

3 pieces, 4+4+4 sides
3STEP 3

Way B: two cuts crossing like a plus sign (4 quadrilaterals)

Two cuts crossing like a plus give 4 quadrilaterals.

4 pieces, each 4 sides
4STEP 4

Way C: snip two opposite corners (2 triangles, 1 hexagon)

Snipping two opposite corners leaves 2 triangles and 1 hexagon.

2 triangles + 1 hexagon = 3 pieces
5STEP 5

Check each way is genuinely different

All five sets differ, so every new way counts.

{3 quad} ≠ {4 quad} ≠ {2 tri,1 hex}
Answer
(A) 3 quadrilaterals / (B) 4 quadrilaterals / (C) 2 triangles + 1 hexagon
Each way uses exactly 2 straight cuts and the piece counts make sense: 2 non-crossing cuts give 3 pieces (Ways A and C), 2 crossing cuts give 4 pieces (Way B and the diagonals example). Adding the sides of all pieces in each way matches what straight cuts can produce, and every multiset of shapes is different from the two given examples.
Takeaway

Just two straight snips on a square can give 3 four-sided pieces, four four-sided pieces, or even two triangles and a six-sided piece -- counting the sides of each piece is all the Grade 2 shape sense you need!

  • What one straight cut does
  • Way A: two parallel cuts (3 quadrilaterals)
  • Way B: two cuts crossing like a plus sign (4 quadrilaterals)
  • Way C: snip two opposite corners (2 triangles, 1 hexagon)
  • Check each way is genuinely different