# 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

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