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## 'Flow Chart' printed from http://nrich.maths.org/

Flow charts give very precise instructions, to perform a task or
calculation.

The flow chart below uses three variables of which you can choose
the starting value for M.

Select several values for M and try to establish what the flow
chart does.

A printable version of the flow chart is available

here
If you start with certain numbers you reach the OUTPUT fairly
quickly, but if you start with other numbers you don't.

e.g. if you start with 144 you reach the OUTPUT a lot sooner than
if you start with 145.

What is special about the numbers that lead to an OUTPUT
quickly?

What is special about the numbers that don't?

Certain values of D divide exactly into M during the
procedure?

What is special about these values of D?

What is special about the value of N that you end up with?

How can the flow chart help you determine whether M is prime?