This is a simple java app that allows you to calculate the area and perimeter of a circle from the number entered.
Just download the attached apk (zipped up) and make sure you have Java installed. Then unzip the file and open up a command line or Terminal to launch. You can launch it in terminal using: java -jar "/path of your files location/CircleAreaNperimeter.jar."
Once the app launches just put in the radius of a circle and click enter. The app will then give you the Area of a circle and the Perimeter of a circle based off the number you've entered. See the assorted screen caps below to see the various possible outputs.
Attached apk file tested on Mac OS X and Windows OS. Screen Caps shown below taken from Mac OS X.