# Circles in Triangle and Rhombus +-- {.image} [[CirclesinTriangleandRhombus.png:pic]] > The circle inside the equilateral triangle has area $16$. What's the area of the circle inside the rhombus? =-- ## Solution by [[Lengths in an Equilateral Triangle]] and [[Area Scale Factor]] +-- {.image} [[CirclesinTriangleandRhombusLabelled.png:pic]] =-- The diameter of the circle inside the [[rhombus]], $E D$, has the same length as the height of the [[equilateral triangle]], $C B$. From the relationships between the [[lengths in an equilateral triangle]], the length of $O B$ is one third that of $C B$. The radius of the circle in the rhombus is therefore $\frac{3}{2}$ times that of the circle in the triangle. The [[area scale factor]] is then $\frac{9}{4}$ and so its area is $\frac{9}{4} \times 16 = 36$.