Advent calendar 2017

20 December

What is the largest number that cannot be written in the form \(10a+27b\), where \(a\) and \(b\) are nonnegative integers (ie \(a\) and \(b\) can be 0, 1, 2, 3, ...)?

Show answer & extension


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


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


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