Calculating volume by known cross sections

In this video I will take you through the concept of building a solid using cross sections perpendicular to the x-y plane. I will also go through the set up, and computation of three such problems. The first involving square cross sections, the second semi-circle cross sections, and the third equilateral triangle cross sections. If you'd like to play around with the applet I made (which I use in the video), just follow this link: https://www.geogebra.org/m/XFgMaKTy