I love how the same algebraic solutions can have a very interesting geometric interpretation.  Math is so beautiful

SimpleStacker

To calculate the inner square area, you take the outer square area, and subtract the area of the triangles:

science

[Daily puzzle] Magic product puzzle

south_korea_ln

![squares](https://i.ibb.co/kmxCLLJ/squares.png)

The area of the outer big square is $$(a + b)^2 = 100$$.

The area of the inner small square is $$a^2 + b^2$$ (from Pythagoras on the triangles).

To calculate the inner square area, you take the outer square area, and subtract the area of the triangles:

$$
a^2 + b^2 = (a + b)^2 - 2(a * b) = 100 - \frac{4*21}{2} = 58
$$
