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### Game of PIG - Sixes

Can you beat Piggy in this simple dice game? Can you figure out Piggy's strategy, and is there a better one?

### Distribution Maker

This tool allows you to create custom-specified random numbers, such as the total on three dice.

### The Random World

Think that a coin toss is 50-50 heads or tails? Read on to appreciate the ever-changing and random nature of the world in which we live.

# Scale Invariance

### Why do this problem?

This problem offers a fascinating exploration into probability density functions for real world data. Whilst the individual steps are quite simple, the problem draws together many strands from distribution theory. The results can be tested on any set of data from any geography book, giving an interesting relevance to the mathematics.

### Possible approach

The first obstacle to overcome is that of notation: can the students understand what is being asked?

The question involves little computation but requires clear thinking of the ideas. This might be facilitated in a group discussion, but might also require individual work.

### Key questions

• If a function is to be a probability density function, what is the major property it must possess?
• What ranges of values will start with a digit $1$?

### Possible extension

Consider carefully why this problem involves 'scale invariance'. Consider the restriction of scale invariance on real world data. Which sets of real world data do you think will be modelled by this distribution? Why?

### Possible support

Skip the first part and provide students with the scale invariant functions. Also, first use the range 1< x < 10 in the last part of the question.
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities can be found here.
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