Download The Magical Mystery of Math

The Magical Mystery of Math
Objective
Students will use the basic operations (addition, subtraction, multiplication, division).
Students will use problem solving skills and the properties of numbers to figure out the
mystery of the math.
Standards
MST 3 E Operations: Add, subtract, multiply and divide whole numbers
MST 3 E Operations: Know single digit addition, subtraction, multiplication, and division
facts
MST 3 E Mathematical Reasoning: Justify their answers and solution processes
Grade Level
As long as the students have a sufficient knowledge of geography (countries),
mathematically this lesson can be taught as young as third grade.
Materials
Two envelopes for each table with the mystery answers
Handout (attached)
Procedure
This lesson is constructed as a small group activity. It would be equally successful as a
whole class activity, individually or as a learning center.
Group the students into groups of three or four. Give each group the two envelopes and a
handout for each student (each student will fill out a handout but they must agree on the
answers). They will fill out each handout and check their answers with the mystery
envelope.
You can add your own variation and style in introducing this lesson. For example tell the
students that you are psychic or magic with special talents. Using math you are able to
determine what they are thinking. As you hand out the envelopes you can preface by saying
that you have had visions of what they will say and placed them in that envelope. The
wonderful thing about this lesson is that you can add your own “flavor” and make it really
fun for the kids.
Trick #1
1.
2.
3.
4.
5.
Think of a number from 1 to 10
Multiply that number by 9
If the number is a 2-digit number, add the digits together
Now subtract 5
Determine which letter in the alphabet corresponds to the number you ended up
with (example: 1=a, 2=b, 3=c,etc.)
6. Think of a country that starts with that letter
7.
8.
9.
10.
Remember the last letter of the name of that country
Think of the name of an animal that starts with that letter
Remember the last letter in the name of that animal
Think of the name of a fruit that starts with that letter
Are you thinking of a Kangaroo in Denmark eating an Orange?
Trick #2
1.
2.
3.
4.
5.
6.
7.
8.
9.
Think of a number from 1 to 10
Multiply that number by 9
If the number is a 2-digit number, add the digits together
Now subtract 4
Determine which letter in the alphabet corresponds to the number you ended up
with (example: 1=a, 2=b, 3=c,etc.)
Think of a country that starts with that letter
Think of an animal that begins with the same letter
Now picture the color of that animal
Think of a fruit that starts with the same letter as the first letter of the animal’s
color
Are you thinking of an Elephant in England eating Grapes?
In the students small groups they can brainstorm ideas try and figure out the mystery of
the math. You can choose to tell (explain) why it works after the students sufficiently
brainstorm for the answers.
As an extension that can bridge to subjects such as geography, students can try to modify
the trick and make their own. They will have to have knowledge of country names. Students
can then try their modified “trick” on their friends or families. If a trick fails students
should have to determine the reasons why it was not as successful as Trick #1.
Description (proof):
By multiplying any number from 1 to 10 by 9, one receives a multiple of 9: 9, 18, 27, 36, 45,
63, 72, 81, 90. One of the properties of any multiple of nine is that, by adding the digits,
one receives a 9 (i.e. (18) 1 + 8 = 9, (27) 2 + 7 = 9, ...). Therefore, all persons taking this
'test' are essentially starting off with the 'random number' 9, and subtracting 5 to get 4.
From this 4, each person taking this test then converts it into an appropriate letter — 'D'.
Therefore, for this 'test', EVERYONE is starting from the letter 'D'.
(98% of people will answer with kangaroos in Denmark when given this exercise.)
Trick #3
Modify the trick for students in higher-level math by adding more steps,
1.
Before the performance, write the words "Denmark," "Elephant" and "Grape" on a
piece of paper. Seal this paper in an envelope.
2. Set the sealed envelope on a table before starting the trick.
3. Ask for a volunteer from the audience and have him or her perform the following
steps:
4. Think of a number between 1 and 9.
5. Subtract 5 from the number.
6. Multiply the difference by 3.
7. Square the product (multiply the product by itself).
8. Add the digits of the new number.
9. If the sum isn't a 1-digit number, add the digits of the new number together. Keep
adding the digits of each new sum until you get a 1-digit number.
10. If the new 1-digit number is less than 5, add 5 to it. If it's greater than 5, subtract
4 from it.
11. Multiply the difference by 2.
12. Subtract 6 from the result.
13. Think of the letter of the alphabet that corresponds to this new number. (A=1, B=2,
etc.)
14. Think of a country that begins with that letter.
15. Think of an animal that begins with the second letter of the country's name.
16. Think of the animal's color.
17. Think of a fruit that begins with the first letter of the animal's color.
18. Once the volunteer has gone through all of this, call attention to the sealed envelope
that has been sitting on the table throughout the proceedings. Ask the volunteer
what country, animal and fruit he or she thought of.
Have the volunteer open the envelope and display its contents. The volunteer, along with the
rest of the audience, will be amazed at the fact that you knew the responses ahead of time.
The Magical Mystery of Math
Write the answer to each question on the line given.
1.
2.
3.
4.
5.
6.
7.
8.
Pick a number between 1 and 10. _______________
Take that number and multiply it by 9. __________
If the number is a two-digit number, add the digits together. ____________
Subtract five from your answer in question #3. _____________
Determine which letter of the alphabet matches up with the number you have left
(answer #4), for example a=1, b=2, c=3 etc. _________
Think of a country that begins with that letter. ____________
Take the last letter of the country and think of animal that begins with that letter.
______________
Finally take the last letter of that animal and name a fruit that begins with that
letter. ____________
Take a look inside the envelope of mystery to see if I can read your mind.
Are you shocked? Should we try another?
1.
2.
3.
4.
5.
6.
7.
8.
9.
Pick a number between 1 and 10. _______________
Take that number and multiply it by 9. __________
If the number is a two-digit number, add the digits together. ____________
Subtract 4 from your answer in question #3. _____________
Determine which letter of the alphabet matches up with the number you have left
(answer #4), for example a=1, b=2, c=3 etc. _________
Think of a country that begins with that letter. ____________
Think of an animal that also begins with that letter. _________
What color is that animal? ___________
Take the first letter of that color and name a fruit that begins with that letter.
______________
Check envelope #2 did I get you again? Can you figure out the mystery of the math? As a
group discuss how I may have done that……….or am I really psychic?