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 2d shapes, 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


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


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