The minimum number of chairs needed for the dinner is 11 chairs
Solution:
Given that,
My widowed granny has 3 kids
Therefore, there is granny and her 3 kids which becomes 4
They are all married with at least 1 kid
The 3 kids are married. Therefore, 3 kids and their partner makes a total of 6 ( which means 3 couples)
They are all married with at least 1 kid. My aunt has 3 nephews
So, there are 4 children in total
The minimum number of chairs needed for the dinner is:
granny + three couples + 4 children = 1 + 6 + 4 = 11
Thus 11 chairs are needed for dinner