Two-way tables can be used to display information relating to several different options and categories.
The following table shows the numbers of right and left-handed children in a school year group of 70 children.
Notice how the totals add up in both directions.
There are 56 right-handed children.
There are 32 right-handed girls.
The probability that a child chosen at random is a right handed girl is 32/70 = 16/35