For a wonderful source of resources, from Tim Brzezinski, try this brilliant GeoGebra book of Open Middle themed problems. Many problems in the GeoGebra book are exact digital analogues of those found on Open Middle’s site, with other problems characteristic of the Open Middle theme. Do check Tim’s collection of GeoGebra resources.

If you are not familiar with Open Middle do explore these excellent problems; you can read more about the type of problems you will find on the site on the About page.

Note you can search by grade using the drop-down menus and you will find a clear index on the right hand side of the home page.

Or perhaps try creating a right -angled triangle: