an image from the US government EPA "Sunwise" program. I converted it from PDF format, and removed all the "sunwise" logos. the source link is here - http://www.epa.gov/sunwise/doc/guide.pdf

Tags: media, clip_art, externalsource, public_domain, image, png, svg, epa, epa_sunwise, ruler, rule, calculator, adding_machine, plus, equals, maths, counting, geometry, epa, epa_sunwise, ruler, rule, calculator, adding_machine, plus, equals, maths, counting, geometry