The Sixth Demonstration: Squaring 6 + 4 into 100
A line halved and extended, with a rectangle-and-square figure totalling 100.
The Sixth demonstration, which Leonardo notes shares the figure of the Fifth, begins with a line divided in half (6 and 6) and the same line extended (6, 6, 4). A small rectangle is joined to a square, the cells carrying 36, 24, 24 and 16 and summing to 100, the square of 10 (= 6 + 4). A short tally in the upper left corner reads 11, 10, 2. The sheet continues the Euclidean dissection of the square of a divided line.
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A line halved and then extended
Leonardo first draws a line divided in half into 6 and 6, then the same line extended and marked 6, 6, 4. The two versions set up the divided quantity whose square the figure below decomposes.
Small rectangle joined to a square, summing to 100
A small rectangle is joined to a square, its cells labelled 36, 24, 24 and 16, which add to 100. This is the square of 10 (= 6 + 4), shown as the sum of the squares and rectangles of the parts.