Puzzle: If the area of the outer square is 100 then what is the area of the inner square?
The inner square touches the outer square at the mid-point of each of its four sides.
Answer:
A square, by definition, has 4 equal sides and it's area is defined as the square of its side.
The outer square has an area of 100 which implies that each of its four sides is of length 10 because 10^2 is 100.
Pythagoras, from ancient Greece, came up with a relationship between the sides of a triangle that has a right angle between two of it's sides. The formula says:
Hypotenuse ^2 = side1^2 + side2^2
(^2 is the sign for squaring)
Note: The hypotenuse is the longest side of the triangle opposite the right angle.
Why do we need this formula?
Because, we need to find the length of one side of the inner square. Each side of the inner square is a hypotenuse in the four triangles surrounding the inner square! Therefore the Pythagoras theorem applies. Let us choose the rightmost triangle at the bottom (see diagram above)
Hypotenuse ^2 = 5^2 + 5^2
Hypotenuse ^2 = 25 + 25 = 50.
5 is the length of each of the two sides that form a right angle in the triangle because the inner square touches the outer square at mid point of its sides.
And because hypotenuse is the same as a side of the inner square, the answer is that the area of the inner square is 50 !!
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