### Elastic Maths

How do you write a computer program that creates the illusion of stretching elastic bands between pegs of a Geoboard? The answer contains some surprising mathematics.

### Logic, Truth Tables and Switching Circuits Challenge

Learn about the link between logical arguments and electronic circuits. Investigate the logical connectives by making and testing your own circuits and fill in the blanks in truth tables to record your findings.

### Truth Tables and Electronic Circuits

Investigate circuits and record your findings in this simple introduction to truth tables and logic.

# Big and Small Numbers in the Living World

##### Stage: 3 and 4 Challenge Level:

Biology makes good use of numbers both small and large. Try these questions involving big and small numbers. You might need to use standard biological data not given in the question. Of course, as these questions involve estimation there are no definitive 'correct' answers. Just try to make your answers to each part as accurate as seems appropriate in the context of question.

1. Estimate how many breaths you will take in a lifetime.

2. Estimate the number of people who live within 1 km of your school.

3. I look through a microscope and see a cell with a roughly circular cross section of 7 microns. Estimate the volume of the cell.

4. The arctic tern migrates from the antarctic to the arctic. Estimate how far an arctic tern flies in its lifetime.

5. Estimate the weight of dog food eaten in England each year.

6. An amoeba doubles in size every 24 minutes. How long will a sample of size about 1mm by 1mm take to cover a petri dish? Do we need to worry too much about the initial size of the sample in this calculation?

7. Estimate how many cells there are in your little finger

8. Estimate the total weight of the pets of everyone in your class

9. How much do you think your brain weighs? How much do you think this weight varies over the course of your life?

10. If current trends continue what will the population of the UK be in ten years' time? Do you think it is reasonable to assume that they will continue? Why?

Extension: Try to improve your estimates by giving a range of numbers between which you know the true answer lies.