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A pink square with one corner folded over so that the tip of the corner touches the centre of the square. The folded over section is a gold right-angled triangle.

Difficulty: Fun

Rosario has a pink square of origami paper. She then folds one corner all the way to the square’s centre to make a new 5-sided shape.

She discovers that the missing corner is exactly the same size as a piece of fairy bread!

How many pieces of fairy bread would it take to cover the whole 5-sided shape?

Need a hint?

When you’re folding paper, the area of folded corner is equal to the space it leaves behind.

Can you use information from the problem to figure out the area of the space left behind?

Brainteaser answer

Rosario can cover the 5-sided origami shape with 7 pieces of fairy bread.

One way to get a handle on this problem is to fold the square into quarters:

The same shape with the folded corner as above with dotted lines showing the outline of the original square. A horizontal and vertical dotted line divide the square into 4 smaller squares. The gold folded corner takes up exactly one half of a smaller square, leaving the other half as a white gap.

We can now see that the origami paper can be divided into 4 equal, smaller squares. And we can also see that the folded corner must be a right-angled triangle that divides one of the smaller squares in half.

We know the white gap can fit one piece of fairy bread, so a second piece will fit on the folded flap. Together, those two pieces cover one small square.

Since there are 4 small squares making up the big origami square, the original origami paper must fit 8 pieces of fairy bread.

But the question actually asks about the folded shape – with its missing one, fairy bread sized, corner. That shape can fit 7 pieces of fairy bread!

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