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How Tall?

A group of children are discussing the height of a tall tree. How would you go about finding out its height?

Discuss and Choose

Stage: 1 and 2 Challenge Level: Challenge Level:1

Discuss and Choose

This activity challenges you to decide on the 'best' number to use in each of the following statements.
You may like to talk to someone else about what you're thinking.  You may need to do some estimating, some calculating and some research.
Please send us your solutions and don't forget to explain how you arrived at your conclusions.
1) There are roughly $10/500/1000$ million domestic cats in the world.
2) On average, cats weigh $1.5/4.5/8$ kg.
3) Domestic cats sleep on average $8-9/13-14/18-19$ hours a day.
4) There are roughly $400/600/800$ million domestic dogs in the world.
5) The average life of a dog is $10-14/14-18/18-20$ years.
6) Dolphins live in groups called pods or schools of up to $12/20/30$ individuals.
7) Adult elephants need to drink about $100/200/400$ litres of water a day.
8) A giraffe's neck is about $120/170/220$ cm long.
9) A giraffe's tail hair is $2/5/10$ times as thick as the average human hair.
10) On average, male lions weigh $180/250/330$ kg.
11) A lion's roar can be heard $8/12/16$  kms away.
12) On average, lions rest for $10/15/20$ hours a day.

Why do this problem?

This activity gives an opportunity to discuss the quantities involved in the statements, and may involve estimation, calculation and/or research. Children will rely not only on what they have learnt from school, but also on information they have picked up from elsewhere. The discussion may well reveal some surprises, particularly in terms of their understanding of different units of measurement. 

Possible approach

The activity could be suitable for small group or whole class discussions, depending on the experiences of the children involved.  You might find it helpful to print off copies of this sheet which has all the statements on it.   The statements could be cut up so that each is on a separate card. 
The role of the adult in this kind of situation is to enable discussion to take place effectively.  It may be that after an initial discussion about each statement, you assign a pair or small group of children a few statements each and invite them to come up with evidence to support their suggested answer.   If possible, encourage them to record as they go along so that they have a reminder of what they did.

Key questions

So, what do "you" think about what "they" have just said?
Tell us your thoughts about ...
So, what do you all think?
Do some of you agree with ...?
If so, why?  Or why not?
How could we be more sure?

Possible extension

Youngsters could create their own challenges in a similar way for others to discuss.

Possible support

Try to help by listening, sharing and offering thoughts where appropriate.