Concentric circles with radii 1, \(\frac{1}{2}\), \(\frac{1}{3}\), \(\frac{1}{4}\), ... are drawn. Alternate donut-shaped regions are shaded.
What is the total shaded area?

Show answer & extension

If you enjoyed this puzzle, check out Sunday Afternoon Maths XIX,
puzzles about geometry, or a random puzzle.


Show me a random puzzle
 Most recent collections 

Advent calendar 2019

Sunday Afternoon Maths LXVII

Coloured weights
Not Roman numerals

Advent calendar 2018

Sunday Afternoon Maths LXVI

Cryptic crossnumber #2

List of all puzzles


circles taxicab geometry regular shapes multiplication division bases hexagons grids ellipses speed unit fractions coordinates rugby mean quadratics digits surds area probabilty routes dominos folding tube maps fractions complex numbers sport differentiation logic triangle numbers volume 2d shapes square roots irreducible numbers median sums proportion wordplay colouring remainders cube numbers factorials gerrymandering chalkdust crossnumber partitions triangles numbers pascal's triangle angles ave square numbers menace parabolas percentages factors geometry 3d shapes perimeter trigonometry lines symmetry graphs crossnumbers integration crossnumber polygons odd numbers cryptic crossnumbers shapes elections dodecagons time clocks products algebra chess books prime numbers spheres christmas doubling arrows cards advent dice sequences chocolate rectangles number planes sum to infinity indices crosswords calculus coins functions perfect numbers balancing people maths cryptic clues tiling probability palindromes floors means integers averages digital clocks addition money range squares games multiples scales star numbers dates the only crossnumber shape


Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2020