# 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

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

Is any of the numbers 11, 111, 1111, 11111, ... a square number?

## What is the sum?

What is \(\displaystyle\frac{1}{\sqrt{1}+\sqrt{2}}+\frac{1}{\sqrt{2}+\sqrt{3}}+...+\frac{1}{\sqrt{15}+\sqrt{16}}\)?