Right.
In the UK, we have a sales tax called VAT (for "value-added tax"). For a while its rate was 17.5%. The way you work that out is: shift the decimal point (10%), halve (5%), halve again (2.5%), and add up :-).
(Tips in the UK are usually about 10%, so that's a bit easier. And now our VAT rate is 20%.)
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