Factors and multiples

problem
Can it be?

Age

16 to 18

Challenge level

When if ever do you get the right answer if you add two fractions by adding the numerators and adding the denominators?
problem
What a joke

Age

14 to 16

Challenge level

Each letter represents a different positive digit AHHAAH / JOKE = HA What are the values of each of the letters?
problem
Millennium leap

Age

11 to 14

Challenge level

How many leap years will there be between 2001 and 3001?
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
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
Coin collection

Age

14 to 16

Challenge level

When coins are put into piles of six 3 remain and in piles of eight 7 remain. How many remain when they are put into piles of 24?
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
Adjacent factors

Age

11 to 14

Challenge level

Two numbers can be placed adjacent if one of them divides the other. Using only $1,...,10$, can you write the longest such list?
problem
Sticky fingers

Age

14 to 16

Challenge level

Ruth wants to puts stickers on the cuboid she has made from little cubes. Will she have any stickers left over?
problem
Rolling along the trail

Age

11 to 14

Challenge level

What could be the scores from five throws of this dice?