mscroggs.co.uk
mscroggs.co.uk

subscribe

Advent calendar 2021

7 December

The picture below shows eight regular decagons. In each decagon, a red triangle has been drawn with vertices at three of the vertices of the decagon.
The area of each decagon is 240. What is the total area of all the red triangles?

Show answer

Archive

Show me a random puzzle
 Most recent collections 

Advent calendar 2024

Advent calendar 2023

Advent calendar 2022

Advent calendar 2021


List of all puzzles

Tags

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

Archive

Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2025