mscroggs.co.uk

mscroggs.co.uk

blog puzzles academic talks contact subscribe ↓ ☰ ↓

Comment

Comments

Comments in green were written by me. Comments in blue were not written by me.

2019-12-17

@Rob: It looks to me like you've made mistakes in questions 1, 6, 8, and 9. The hints from the back of the pdf might help:

1. How many numbers between 1 and 10,000 have 1 as their final digit? How many have 1 as their penultimate digit?

6. How many ways can you write 1? 2? 3? 4? 5? What's the pattern?

8. How many zeros does 10! end in? How many zeros does 20! end in? How many zeros does 30! end in?

9. Carolâ€™s sum is odd. What does this tell you about the 5- and 6-digit numbers?

Matthew
on /blog/70

×3

×3

×4

×3

×4

Archive

Show me a random blog post

2025

Jun 2025

A nonogram alphabet

Mar 2025

How to write a crossnumber

Jan 2025

Christmas (2024) is over
Friendly squares

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

Tags

machine learning football reddit big internet math-off errors simultaneous equations pizza cutting nine men's morris folding tube maps realhats draughts map projections matrix of cofactors captain scarlet national lottery sorting final fantasy newcastle programming finite group london harriss spiral crosswords craft pascal's triangle plastic ratio propositional calculus folding paper statistics logo youtube sobolev spaces video games puzzles 24 hour maths zines ucl inline code determinants manchester accuracy estimation polynomials logic cambridge go games raspberry pi matt parker hexapawn noughts and crosses preconditioning european cup mathsjam rhombicuboctahedron bodmas guest posts speed latex electromagnetic field signorini conditions inverse matrices advent calendar frobel asteroids sound recursion numerical analysis braiding convergence datasaurus dozen edinburgh dataset chebyshev gerry anderson radio 4 tmip bubble bobble tennis matrices news royal institution crossnumber graph theory regular expressions coins turtles chalkdust magazine correlation error bars pythagoras oeis palindromes dates menace christmas runge's phenomenon probability chess graphs royal baby gather town alphabets pi approximation day approximation ternary live stream mathslogicbot game show probability hats data binary phd boundary element methods flexagons finite element method trigonometry bots rugby the aperiodical pac-man triangles anscombe's quartet fractals python a gamut of games crossnumbers wave scattering fence posts christmas card mean geometry dragon curves geogebra hannah fry hyperbolic surfaces bempp kings london underground numbers weather station arithmetic misleading statistics golden spiral reuleaux polygons countdown standard deviation cross stitch exponential growth stickers nonograms databet mathsteroids crochet friendly squares gaussian elimination weak imposition stirling numbers fonts pi dinosaurs interpolation matrix of minors logs data visualisation quadrilaterals talking maths in public martin gardner people maths light sport matrix multiplication javascript wool manchester science festival php books golden ratio world cup platonic solids game of life curvature computational complexity squares

Archive

Show me a random blog post
▼ show ▼

© Matthew Scroggs 2012–2025