Lego can be a great way to teach your child multiplication and division.  One way to do this is to give them a number and ask them to represent this as a 'block' or rectangle.  For example: if you give them the number 30, they need to look at the circles on the top of the lego and then represent this number according to which two numbers you could multiply together to make it (the one shown in the picture is a 6 x 5 block).  You could also use this method for helping solve area problems (which often crop up in the 11 plus).  Children may be asked to work out the dimensions of a rectangle that has an area of 20cm squared.  The second rectangle here shows how those dimensions could be 4 x 5.  There are some good worksheets on area on this website: http://www.primaryresources.co.uk/maths/mathsE4.htm