{"slug":"circle-area","tier":1,"subject":"geometry","title":"Circle Area","description":"Area from radius.","files":[{"filename":"CIRCLE.py","content":"def p(s):print(s)\ndef f():\n r=float(input(\"r:\"))\n a=3.14159265*r*r\n p(\"A=\"+str(a))\nf()"}],"testCases":[{"id":"r-2","inputs":["2"],"expectedContains":["A=12.5663"]}],"usage":"Launch `CIRCLE` from the `prgm` key. The program prompts once for the radius.\n\n1. `r:` — enter the radius (any units; the output area is in those units squared).\n2. Press `enter`.\n3. You'll see `A=` with the area value.\n\nUses π ≈ 3.14159265, so results match a standard 8-digit calculator.","example":{"problem":"A circular table has a radius of 2 feet. What's its area in square feet?","walkthrough":"1. Run `CIRCLE`.\n2. At `r:` type **2**, press `enter`.\n3. Output: `A=12.5663706`.\n\nThe area is ≈ 12.57 ft². Verify: π·r² = 3.14159 · 4 = 12.566. ✓"}}