Monday, March 28, 2011

Tutoring: per cent

So, the next topic I'll be teaching my student is percent. Before we start cranking the Singapore Math, I plan a little dialogue like this:

Q.  Why do we call pennies "cents"?

A.  Because there are 100 to the dollar.

Q.  How many years in a century?

A.  100.

Q.  What does "cent" mean?

A.  100.

Q.  What does "per cent" mean?

A.  "for 100".

Digression (if we have time):

Q.  British money also contains pennies, but they are never referred to as "cents".  Why?

A.  Because, historically, there were more than 100 pence to the pound.  For centuries, Britain had a system where there were 20 shillings to the pound, and 12 pence to the shilling. 

Q.  How many pence were there to the pound?

A.  12 x 20  = 240.

Since 1971, Britain has been using a modernized currency, so they now have 100 pence to the pound.

Extra credit for old folks (I might ask my student's parents): what Beatles song contains an oblique reference to the old currency system?

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