# Puzzles

## Archive

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

#### Sunday Afternoon Maths LXVII

Coloured weightsNot Roman numerals

#### Advent calendar 2018

#### Sunday Afternoon Maths LXVI

Cryptic crossnumber #2#### Sunday Afternoon Maths LXV

Cryptic crossnumber #1Breaking Chocolate

Square and cube endings

List of all puzzles

## Tags

rugby triangle numbers scales complex numbers games sums symmetry 3d shapes number speed colouring balancing coins angles differentiation parabolas geometry numbers shapes factors remainders means books factorials planes dodecagons circles sequences clocks integers integration probability square numbers odd numbers quadratics crosswords addition squares division volume area multiplication folding tube maps regular shapes palindromes star numbers dice square roots crossnumbers cards lines digits irreducible numbers mean chess advent indices fractions polygons time partitions cryptic clues logic coordinates floors prime numbers triangles algebra taxicab geometry surds doubling ave rectangles sum to infinity arrows dates averages unit fractions menace graphs chocolate hexagons percentages spheres proportion bases money 2d shapes routes perimeter people maths trigonometry shape chalkdust crossnumber wordplay cube numbers perfect numbers functions calculus probabilty grids multiples christmas pascal's triangle sport cryptic crossnumbers ellipses## Not Roman numerals

The letters \(I\), \(V\) and \(X\) each represent a different digit from 1 to 9. If

$$VI\times X=VVV,$$
what are \(I\), \(V\) and \(X\)?

## Backwards fours

Source: FiveThirtyEight

If A, B, C, D and E are all unique digits, what values would work with the following equation?

$$ABCCDE\times 4 = EDCCBA$$## 10 December

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

## 17 December

In March, I posted the puzzle One Hundred Factorial, which asked how many zeros 100! ends with.

What is the smallest number, n, such that n! ends with 50 zeros?