Question

Peter is making an "X marks the spot" flag for a treasure hunt. The flag is made of a square white flag with sides of 121212 inches. He will make the "X" by stretching red ribbon diagonally from corner to corner.
How many inches of ribbon will Peter need to make the "X"?
Round your answer to the nearest inch.

Answer 1

He will need 17 inches of ribbon.

The diagonal splits the square into two right triangles.  We can then use the Pythagorean theorem to find the length of the diagonal (the hypotenuse of the triangle):

12² + 12² = x²
144 + 144 = x²
288 = x²

Take the square root of both sides:
√288 = √x²
16.97 = x
17≈x