Final answer:
Thales likely measured a pyramid's height by comparing the shadows of the pyramid and a known stick, which demonstrates a practical application of geometry involving similar triangles without complex tools.
Step-by-step explanation:
Thales is believed to have measured the height of a pyramid using the method of stick and shadow. By utilizing the principles of similar triangles, Thales could compare the lengths of the shadow of the pyramid and that of a stick, whose height he already knew, when the Sun's rays were at the same angle. This practical application of geometry did not require complicated tools, hence the correct answer is Using a stick and shadow.
History tells us that Thales excelled in combining his wisdom of the natural world with pragmatic applications, such as using scientific knowledge to have a successful year with olive sales. Like Eratosthenes, who calculated the Earth's circumference by measuring shadows in different cities, Thales's approach to solving practical problems involved an understanding of geometry and the natural behavior of light and shadows.