110 Years On
110 Years On
Pupils use mathematical reasoning to estimate the number of descendants a girl who lived 110 years ago might have today.
- National Curriculum levels 5 to 8
- About 45 minutes
- Additional paper plus access to a calculator if requested
Key Processes involved
- Simplify the information given, choose a model, then make assumptions to complete the model.
- Use their model to calculate the potential number of descendants.
- Communicating and reflecting
- Present arguments summarising their onclusions and reflect on the validity of their results.
You may wish to show the task on a whiteboard and talk about the concept of descendants
- In this task, there is a photograph of a girl, about your age, who lived 110 years ago. She grew up, had children, who had their own children and so on.
- A family party is being planned for all her descendants. Your task is to make a good estimate of how many descendants you might expect her to have.
- You are given some facts – think about why there are there, and use them!
- Show your working so I can know what you did and how you reached your answer.
The task requires multiplicative calculations to represent changes over time.
The following probing questions may be helpful:
- What assumptions have you made?
- When you are thinking about all her descendants over the 110 years, are there any other factors you need to consider?
- Have you made sure you have thought of all her descendants?
There are several assumptions needed for the task:
- How many children the girl had and when.
- The average age of giving birth and whether this changes over time.
- When and how, during the 20th century, the birth rate changed.
- The proportion of her descendants that conformed to the average birth rates.
- At what age people die, and so how many descendants are still alive for the party.
Note: If pupils use more than 25 years between generations, they are likely to work with only 3 generations so may consider just counting. If so, they should be encouraged to consider a smaller number of years between generations.