# Puzzles

## Archive

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#### 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

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

What is the maximum number of lines that can be formed by the intersection
of 30 planes?

## Two lines

Let A and B be two straight lines such that the gradient of A is the y-intercept of B and the y-intercept of A is the gradient of B (the gradient and y-intercept of A are not the same). What are the co-ordinates of the point where the lines meet?