# Blog

## Archive

Show me a random blog post**2019**

**2018**

**2017**

**2016**

**2015**

**2014**

**2013**

**2012**

## Tags

weather station flexagons countdown manchester nine men's morris rugby royal baby oeis reuleaux polygons curvature noughts and crosses pac-man map projections mathsteroids fractals pizza cutting approximation asteroids binary data video games rhombicuboctahedron accuracy interpolation menace world cup radio 4 captain scarlet polynomials london matt parker light statistics golden spiral aperiodical big internet math-off dates news ternary plastic ratio puzzles php chess geometry palindromes the aperiodical a gamut of games braiding christmas card national lottery chebyshev craft hats raspberry pi european cup people maths stickers coins machine learning programming bubble bobble sport dataset sound london underground graph theory folding tube maps frobel inline code dragon curves draughts books cross stitch error bars platonic solids probability latex python go game show probability javascript reddit final fantasy twitter pythagoras propositional calculus arithmetic golden ratio harriss spiral trigonometry game of life speed logic hexapawn bodmas estimation chalkdust magazine football gerry anderson misleading statistics electromagnetic field martin gardner realhats wool manchester science festival sorting mathslogicbot folding paper triangles tennis games christmas**2018-12-08**

## Christmas card 2018

Just like last year and the year before, TD and I spent some time in November this year designing a Chalkdust puzzle Christmas card.

The card looks boring at first glance, but contains 10 puzzles. By splitting the answers into pairs of digits, then drawing lines between the dots on the cover for each pair of digits (eg if an answer is 201304, draw a line from dot 20 to dot 13 and another line from dot 13 to dot 4), you will reveal a Christmas themed picture. Colouring the region of the card labelled R red or orange will make this picture even nicer.

If you want to try the card yourself, you can download this pdf. Alternatively, you can find the puzzles below and type the answers in the boxes. The answers will be automatically be split into pairs of digits, lines will be drawn between the pairs, and the red region will be coloured...

If you enjoy these puzzles, then you'll almost certainly enjoy this year's puzzle Advent calendar.

1. | What is the smallest four digit number whose digits add up to 6? | Answer |

2. | What is the length of the hypotenuse of a right angled triangle whose two shorter sides have lengths 152,560 and 114,420? | Answer |

3. | What is the lowest common multiple of 1346 and 196? | Answer |

4. | What is the sum of all the odd numbers between 0 and 698? | Answer |

5. | How many numbers are there between 100 and 10,000 that contain no 0, 1, 2, or 3? | Answer |

6. | How many factors (including 1 and the number itself) does the number \(2^{13}\times3^{19}\times5^9\times7^{39}\) have? | Answer |

7. | In a book with pages numbered from 1 to 16,020,308, what do the two page numbers on the centre spread add up to? | Answer |

8. | You think of a number, then make a second number by removing one of its digits. The sum of these two numbers is 18,745,225. What was your first number? | Answer |

9. | What is the largest number that cannot be written as \(13a+119b\), where \(a\) and \(b\) are positive integers or 0? | Answer |

10. | You start at the point (0,0) and are allowed to move one unit up or one unit right. How many different paths can you take to get to the point (7,6)? | Answer |

### Similar posts

Christmas card 2017 | Christmas card 2016 | Christmas (2018) is over | Christmas (2018) is coming! |

### Comments

Comments in green were written by me. Comments in blue were not written by me.

**Add a Comment**

2018-12-17Matthew