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.

Some more rows and columns have been added to the table below.

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 add even more columns to the table. 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

You can find more short problems, arranged by curriculum topic, in our short problems collection.