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MATH-MAGIC NUMBER 1
Card Values:
Ace = 1
2=2
3=3…
10 = 10
J = 11
Q = 12
K = 13
For this activity, we’ll select two volunteers. Each will choose a card
from the deck and show the rest of the class. The class will verify that
the calculations are correct.
The first person will do the following:
Take the value of your card, multiply it by 4, add 5, then multiply by 5.
The second person will do the following:
Take the value of the card, multiply by 2, subtract 10, then divide by 2.
Neither person will tell me their individual numbers, but instead, they
will take the resulting number from each part and add them together.
When finished, verify with the class that this is the correct value. Then
tell JUST this value.
MATH-MAGIC NUMBER 2
Doug will show you a
card trick. You need to
determine how it is
done and why it works
(if it really does always
work). This trick will
involve three cards
along with the
operations of addition
and division.
Card Values: Ace = 1, 2 = 2, … 9 = 9,
Ten/Jack/Queen/King = 0
Draw three cards – only requirement is that all three must have different
face values (so you couldn’t have a Jack and a Queen since both are
worth 0, and you couldn’t have a pair of 4’s, etc). Once you have them,
arrange them to form all possible 2 digit numbers. It is okay to have a
two digit number that starts with a 0.
Add up all of these two digit numbers and write down the sum. Then
take the original three face values and add them together. Divide the
larger sum by the smaller sum and find the quotient (the answer from the
division problem).
What is your result? Why?
MATH-MAGIC NUMBER 3
Doug will show you a card trick. You need to
determine how it is done and why it works (if it
really does always work). This trick will
involve three cards along with the operations of
addition and subtraction.
Card Values: Ace = 1, 2 = 2, … 9 = 9,
Ten/Jack/Queen/King = 0
Draw three cards – only requirement is that you can’t end with 3
of a kind. Once you have them, arrange them to form the largest
possible 3 digit number, and the smallest possible 3 digit
number (it is okay if the number ends up 005, this is still a 3digit number).
Now take the large number and subtract the smaller number –
this will form a 3 digit number (again, it is okay if the first digit
is a 0).
With this new number, write it
backwards (abc would become cba).
Then add these two together.
What is your result? Why?