12 December

The diagram to the left shows a large black square. Inside this square, two red squares have been drawn. (The sides of the red squares are parallel to the sides of the black square; each red square shares a vertex with the black square; and the two red squares share a vertex.) A blue quadrilateral has then been drawn with vertices at two corners of the black square and the centres of the red squares.
The area of the blue quadrilateral is 167. What is the area of the black square?

Show answer


Show me a random puzzle
 Most recent collections 

Advent calendar 2020

Advent calendar 2019

Sunday Afternoon Maths LXVII

Coloured weights
Not Roman numerals

Advent calendar 2018

List of all puzzles


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


Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2021