Factors and multiples

problem
Find from factors

Age

11 to 14

Challenge level

Weekly Problem 35 - 2006
A number has exactly eight factors, two of which are 21 and 35. What is the number?
problem
Essential supplies

Age

14 to 16

Challenge level

Chocolate bars come in boxes of 5 or boxes of 12. How many boxes do you need to have exactly 2005 chocolate bars?
problem
Prime order

Age

11 to 14

Challenge level

Weekly Problem 24 - 2006
How many of the rearrangements of the digits 1, 3 and 5 give prime numbers?
problem
Diagonal product Sudoku

Age

11 to 16

Challenge level

Given the products of diagonally opposite cells - can you complete this Sudoku?
problem
Product Sudoku

Age

11 to 16

Challenge level

The clues for this Sudoku are the product of the numbers in adjacent squares.
problem
Stair climb

Age

11 to 14

Challenge level

Three people run up stairs at different rates. If they each start from a different point - who will win, come second and come last?
problem
Seven flipped

Age

7 to 11

Challenge level

Investigate the smallest number of moves it takes to turn these mats upside-down if you can only turn exactly three at a time.
problem
Data chunks

Age

14 to 16

Challenge level

Data is sent in chunks of two different sizes - a yellow chunk has 5 characters and a blue chunk has 9 characters. A data slot of size 31 cannot be exactly filled with a combination of yellow and blue chunks, explore what sizes near to 31 can, or cannot, be exactly filled.
problem
Different by one

Age

14 to 16

Challenge level

Can you make lines of Cuisenaire rods that differ by 1?
problem
Same length trains

Age

5 to 7

Challenge level

How many trains can you make which are the same length as Matt's and Katie's, using rods that are identical?