Growing Families

a) To find the average number of children per family, we need to know the total number of children, and divide this by the total number of families.

Number of children	1	2	3	4	5	total
Number of families	6	13	9	4	1	33
Total number of children in families this size	1$\times$6  = 6	2$\times$13 = 26	3$\times$9  = 27	4$\times$4  = 16	5$\times$1  = 5	80

80$\div$33 = 2.42


b) To find the average number of siblings, we need to know the total number of siblings of all of the children combined, and divide this by the total number of children.
 

Number of children	1	2	3	4	5	total
Number of families	6	13	9	4	1
Total number of children in families this size	1$\times$6  = 6	2$\times$13 = 26	3$\times$9  = 27	4$\times$4  = 16	5$\times$1  = 5	80
Number of siblings each child in this size family has	0	1	2	3	4
Total number of siblings in families this size	0$\times$6  = 0	1$\times$26 = 26	2$\times$27 = 54	3$\times$16 = 48	4$\times$5  = 20	148

148$\div$80 = 1.85