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'Clickety Click and All the Sixes' printed from https://nrich.maths.org/
Why do this
problem?
A non-standard problem based on place value and summing geometric
series requiring simple manipulation of a numerical
expression.
Possible approach
A short problem suitable as a lesson starter.
Key questions
Can you write the 10 digit number $6666666666$ as a geometric
series?
Can you sum this series?
Can you do the same for any number that is a 'string of
sixes'?
Possible extension
For a discussion of a generalisation of this problem see
Sum The Series.