mscroggs.co.uk
mscroggs.co.uk

subscribe

Puzzles

The blue-eyed sisters

If you happen to meet two of the Jones sister (two sisters chosen at random from all the Jones sisters), it is exactly an even-money bet that both will be blue-eyed. What is your best guess of the total number of Jones sisters?

Show answer & extension

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

Archive

Show me a random puzzle
 Most recent collections 

Advent calendar 2023

Advent calendar 2022

Advent calendar 2021

Advent calendar 2020


List of all puzzles

Tags

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

Archive

Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2024