Factors and multiples

problem

Trailing Zeros

Age

11 to 14

Challenge level

How many zeros does 50! have at the end?
problem

Transposition Cipher

Age

11 to 16

Challenge level

Can you work out what size grid you need to read our secret message?
problem

Star Product Sudoku

Age

11 to 16

Challenge level

The puzzle can be solved by finding the values of the unknown digits (all indicated by asterisks) in the squares of the $9\times9$ grid.
problem

Times Right

Age

11 to 16

Challenge level

Using the digits 1, 2, 3, 4, 5, 6, 7 and 8, mulitply a two two digit numbers are multiplied to give a four digit number, so that the expression is correct. How many different solutions can you find?
problem

Substitution Transposed

Age

11 to 16

Challenge level

Substitution and Transposition all in one! How fiendish can these codes get?
problem

LCM Sudoku II

Age

11 to 18

Challenge level

You are given the Lowest Common Multiples of sets of digits. Find the digits and then solve the Sudoku.
problem

What Does It All Add Up To?

Age

11 to 18

Challenge level

If you take four consecutive numbers and add them together, the answer will always be even. What else do you notice?
problem

N000ughty

Age

14 to 16

Challenge level

How many noughts are at the end of these giant numbers?
problem

Mod 3

Age

14 to 16

Challenge level

Prove that if a^2+b^2 is a multiple of 3 then both a and b are multiples of 3.
problem

A Biggy

Age

14 to 16

Challenge level

Find the smallest positive integer N such that N/2 is a perfect cube, N/3 is a perfect fifth power and N/5 is a perfect seventh power.