Factors and multiples

problem

Mathdoku

Age

7 to 11

Challenge level

Complete the Mathdoku grid using the clues. Can you convince us that the number you have chosen for each square has to be correct?
problem

Pebbles

Age

7 to 11

Challenge level

Place four pebbles on the sand in the form of a square. Keep adding as few pebbles as necessary to double the area. How many extra pebbles are added each time?
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

What Two ...?

Age

7 to 11

Challenge level

56 406 is the product of two consecutive numbers. What are these two numbers?
problem

Spelling Circle

Age

7 to 11

Challenge level

Find the words hidden inside each of the circles by counting around a certain number of spaces to find each letter in turn.
problem

Sets of Numbers

Age

7 to 11

Challenge level

How many different sets of numbers with at least four members can you find in the numbers in this box?
problem

A Square Deal

Age

7 to 11

Challenge level

Complete the magic square using the numbers 1 to 25 once each. Each row, column and diagonal adds up to 65.
problem

Sets of Four Numbers

Age

7 to 11

Challenge level

There are ten children in Becky's group. Can you find a set of numbers for each of them? Are there any other sets?
problem

Crossings

Age

7 to 11

Challenge level

In this problem we are looking at sets of parallel sticks that cross each other. What is the least number of crossings you can make? And the greatest?
problem

Which Numbers? (2)

Age

7 to 11

Challenge level

I am thinking of three sets of numbers less than 101. Can you find all the numbers in each set from these clues?