2 December

What is the maximum number of lines that can be formed by the intersection of 30 planes?

Two lines

Let A and B be two straight lines such that the gradient of A is the y-intercept of B and the y-intercept of A is the gradient of B (the gradient and y-intercept of A are not the same). What are the co-ordinates of the point where the lines meet?

Show answer & extension


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


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


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