Nobody prints a formula for THIS floor — and nobody needs to. Every odd floor is friendly shapes holding hands: slice it into rectangles, triangles and half-circles, work each piece, and add. A hole works the same way backwards: find the cut-out's area and SUBTRACT it. The slicing plan is the math; the arithmetic just follows.

And guess before you compute — one quick “is this closer to 4, 40 or 400 square metres?” A bedroom is ten-something; a classroom is fifty-ish; a gym is hundreds. Five seconds of guessing catches the doubled triangle and the un-subtracted hole before they cost you marks.