How much charge is left? Percentage of an Amount

I built this a while ago on Geogebra.  I usually use it with mini-whiteboards as a flexible way to do AfL on percentage of an amount.  You can select what is shown using the tick boxes, usually revealing the “answer” by ticking the third box – “Show amount”.

If you click the image above, it will open in GeoGebra Tube.  If you would rather download the .ggb file, click here.