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Q&A #2599

Teachers' Lounge Discussion: Classroom Openers

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From: Joe <josephsweeney@rcn.com>
To: Teacher2Teacher Public Discussion
Date: 2004071820:54:49
Subject: Re: Re: Re: Classroom Openers



I am reminded of an old trick that might amuse you and egage the
students.  Have them pick a two digit number...

Now begin to play with them; having them add, multiply, etc. to the
number.  In the end you can have them reach a specific number or the
one they chose originally.

You can work out your routine ahead of time by using algebra.

Let the first digit of any number be A and the second digit (or one's
column) be B.  Then any student choice will equal 10A+B.

Now play with the algebra.

Divide their number by 2...

(10A+B)/2

multiply it by 8

40A+4B

subtract 20 and then divide by 2 : (40A+4B-20)/2 = 20A+2B-10

Add 10

multiply by three

divide by six

etc.

Playing with three digits might mean letting them use their calculator
and just use 100A+10B+C in your calculations.


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