Multiplication and division

problem
X is 5 squares

Age

7 to 11

Challenge level

Can you arrange 5 different digits (from 0 - 9) in the cross in the way described?
problem
Starfish spotting

Age

5 to 7

Challenge level

How many starfish could there be on the beach, and how many children, if I can see 28 arms?
problem
The amazing splitting plant

Age

5 to 7

Challenge level

Can you work out how many flowers there will be on the Amazing Splitting Plant after it has been growing for six weeks?
problem
Magic plant

Age

5 to 7

Challenge level

On Friday the magic plant was only 2 centimetres tall. Every day it doubled its height. How tall was it on Monday?
problem
Double digit

Age

11 to 14

Challenge level

Choose two digits and arrange them to make two double-digit numbers. Now add your double-digit numbers. Now add your single digit numbers. Divide your double-digit answer by your single-digit answer. Try lots of examples. What happens? Can you explain it?
problem
Adding all nine

Age

11 to 14

Challenge level

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!
problem
Magic constants

Age

7 to 11

Challenge level

In a Magic Square all the rows, columns and diagonals add to the 'Magic Constant'. How would you change the magic constant of this square?
problem
It figures

Age

7 to 11

Challenge level

Suppose we allow ourselves to use three numbers less than 10 and multiply them together. How many different products can you find? How do you know you've got them all?
problem
Sometimes we lose things

Age

7 to 11

Challenge level

Well now, what would happen if we lost all the nines in our number system? Have a go at writing the numbers out in this way and have a look at the multiplications table.
problem
Doplication

Age

7 to 11

Challenge level

We can arrange dots in a similar way to the 5 on a dice and they usually sit quite well into a rectangular shape. How many altogether in this 3 by 5? What happens for other sizes?