mscroggs.co.uk
mscroggs.co.uk

subscribe

Puzzles

N

Consider three-digit integers \(N\) such that:
(a) \(N\) is not exactly divisible by 2, 3 or 5.
(b) No digit of \(N\) is exactly divisible by 2, 3 or 5.
How many such integers \(N\) are there?

Show answer & extension

If you enjoyed this puzzle, check out Sunday Afternoon Maths XVII,
puzzles about factors, or a random puzzle.

Archive

Show me a random puzzle
 Most recent collections 

Advent calendar 2024

Advent calendar 2023

Advent calendar 2022

Advent calendar 2021


List of all puzzles

Tags

elections regular shapes probabilty binary division christmas games bases graphs angles balancing differentiation coordinates axes numbers shape floors sum to infinity symmetry numbers grids triangles mean dates hexagons the only crossnumber products factors digital products geometric mean square grids colouring decahedra perimeter integration rectangles parabolas scales functions quadratics partitions perfect numbers sport factorials menace consecutive numbers circles number polynomials multiplication probability proportion grids digital clocks complex numbers crosswords odd numbers cubics triangle numbers tournaments consecutive integers folding tube maps lines squares tiling area speed median cryptic clues fractions indices arrows determinants powers addition cube numbers digits time medians sets neighbours cryptic crossnumbers square roots shapes prime numbers dodecagons tangents routes multiples palindromes money advent albgebra square numbers averages percentages books trigonometry irreducible numbers expansions dominos gerrymandering geometry logic cards doubling matrices calculus ellipses people maths algebra volume sums chalkdust crossnumber even numbers 3d shapes quadrilaterals ave remainders polygons pascal's triangle combinatorics planes integers range pentagons clocks sequences rugby 2d shapes means taxicab geometry crossnumbers geometric means coins unit fractions chess spheres star numbers surds dice chocolate wordplay

Archive

Show me a random puzzle
▼ show ▼
© Matthew Scroggs 2012–2025