Question

Mike has two containers, One container is a rectangular prism with width 2 cm, length 4cm, and height 10cm. The other is a cylinder with a radius of 1cm and height 10cm. Both containers sit on flat surfaces. Water has been poured into two containers so that the height of the water in two containers is 80 cubed cm, then the height of the water in each container is?

Answer 1

so, we know both the rectangular prism and the cylinder got filled up to a certain height each, the same height say "h" cm.

we know the combined volume of both is 80 cm³, so let's get the volume of each, sum them up to get 80 then.

$\bf \stackrel{\stackrel{\textit{volume of a}}{\textit{rectangular prism}}}{V=Lwh}~~ \begin{cases} L=length\\ w=width\\ h=height\\[-0.5em] \hrulefill\\ L=4\\ w=2\\ \end{cases}~\hspace{2em}\stackrel{\textit{volume of a cylinder}}{V=\pi r^2 h}~~ \begin{cases} r=radius\\ h=height\\[-0.5em] \hrulefill\\ r=1 \end{cases} \\\\[-0.35em] \rule{34em}{0.25pt}$

$\bf \stackrel{\textit{prism's volume}}{(4)(2)(h)}~~+~~\stackrel{\textit{cylinder's volume}}{(\pi )(1)^2(h)}~~=~~80 \\\\\\ 8h+\pi h=80\implies h(8+\pi )=80\implies h=\cfrac{80}{8+\pi }\implies h\approx 7.180301999$