To calculate the $y$-coordinate of the centroid ($\bar{y}$) of a triangular area, we use the formula:

$\bar{y} = \frac{h}{3}$

Where $h$ is the height of the triangle (measured perpendicular to the base).

Details from the problem:

• The height $h$ of the triangle is $90 \, \text{mm}$, measured along the $y$-axis.
• The base lies along the $x$-axis.

Substitute $h = 90 \, \text{mm}$ into the formula:

$\bar{y} = \frac{90}{3} = 30 \, \text{mm}$

However, the height $h$ must account for the full triangular shape and distribution. For this specific case:

[ \bar{y)== Use self-stage