Download Algebra Magic

Algebra Magic
Turning words into equations
Think of a number.
Write it down.
Don’t show it to anyone!
Add 5 to your number
Multiply the result by 2
Subtract 4 from that result.
Divide the answer by 2
Subtract the original number.
Don’t show the answer to
anyone!
Now say the magic words to
make your answer appear on
this screen:
I love math!
The result is:
3
How did this work?
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Think of a number.
Write it down.
Don’t show it to anyone!
Take one of the 2 larger objects out of
your plastic bag and put it on the table in
front of you.
Add 5 to your number
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Take five discs out of the bag and put
them with the larger object.
Each Disc stands for 1.
What do you have in front of you?
Your number + 5
N+5
Multiply the result by 2
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Take the other large object and the other
5 discs out of your bag and place those in
front of you on the table, so that you have
twice as many objects as they had before.
What do you have in front of you?
Two of your number + 10
2N + 10
Subtract 4 from that result.

Take away 4 chips from the amount you
have
What amount do you have now?
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Twice my original number + 6
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2N + 6
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Divide the answer by 2
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Divide the amount into 2 equal piles and
keep just one of the piles.
This leaves their original object + 3
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N+3
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Subtract the original number.
Don’t show the answer to anyone!
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Take away your original number.
What are you left with?
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3 discs
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3
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Variables
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A variable is a symbol used to represent
an amount when you don’t know what the
amount is or when the amount isn’t
always the same.
Several of you were using the same color
block for your original numbers, which
were all different.
Write these phrases using variables
and numbers:
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The sum of a number and 7
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7 greater than a number
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N+7
7 less than a number
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N+7
N–7
A number decreased by 7
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N-7
Write these phrases using variables
and numbers:
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Twice a number
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9 times the opposite of a number
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9(-n) = -9(n)
The sum of twice a number and (-8)
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2n
2n + -8
4 times the sum of twice a number and -3
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4[2n + (-3)]