# Puzzles

## Archive

Show me a random puzzle**Most recent collections**

#### Sunday afternoon maths LXIV

Is it equilateral?Cube multiples

#### Advent calendar 2017

#### Sunday afternoon maths LXII

What's the star?#### Sunday afternoon maths LXI

XYZList of all puzzles

## Tags

time geometry 2d shapes 3d shapes numbers spheres trigonometry complex numbers algebra lines graphs coordinates odd numbers fractions differentiation calculus folding tube maps ellipses triangle numbers money bases triangles squares area square numbers chess probability circles averages speed sport multiples dates factors parabolas functions logic cards games people maths shape prime numbers irreducible numbers probabilty angles proportion dice integration sum to infinity dodecagons hexagons multiplication factorials coins shapes regular shapes colouring grids floors integers rugby crosswords percentages digits sums christmas rectangles clocks menace routes taxicab geometry remainders chalkdust crossnumber palindromes sequences means unit fractions division square roots surds doubling quadratics indices planes volume number partitions ave pascal's triangle mean advent symmetry arrows addition cube numbers star numbers perfect numbers 2dshapes## 17 December

Arrange the digits 1-9 in a 3×3 square so that every row makes a three-digit square number, the first column makes a multiple of 7 and the second column makes a multiple of 4.
The number in the third column is today's number.

square | |||

square | |||

square | |||

multiple of 7 | multiple of 4 | today's number |

## 16 December

There are 204 squares (of any size) in an 8×8 grid of squares. Today's number is the number of rectangles (of any size) in a 2×19 grid of squares

## 15 December

The string

*ABBAABBBBB*is 10 characters long, contains only*A*and*B*, and contains at least three*A*s.Today's number is the number of different 10 character strings of

*A*s and*B*s that have at least three*A*s.## 14 December

There are 204 squares (of any size) in an 8×8 grid of squares. Today's number is the number of squares in a 13×13 grid of squares

## 13 December

A book has 754 pages (numbered 1 to 754: page 1 is on the left of the first double page spread, and page 754 is on the right of the final double page spread). What do the page numbers of the middle two-page spread add up to?

## 12 December

Put the digits 1 to 9 (using each digit exactly once) in the boxes so that the sums are correct. Today's number is the product of the numbers in the red boxes.

+ | + | = 17 | |||

+ | + | + | |||

+ | + | = 7 | |||

+ | + | + | |||

+ | + | = 21 | |||

= 11 | = 20 | = 14 |

## 11 December

Two more than today's number is the reverse of two times today's number.

## 10 December

How many zeros does 1000! (ie 1000 × 999 × 998 × ... × 1) end with?