1. April Fool Math
Ask all students/participants to write down a three-digit number.
The first and third digits must differ by more than one.
Example : 264
Now reverse the digits to form a second number.
Example : 462
Subtract the smaller number from the larger one.
Example : 462—264 = 198
Now reverse the digits in the answer you got in step 3 and add it to that number.
Example : 891 + 198 = 1089
Multiply the number by one million.
Example : 1089 x 1000000 = 1089000000
Subtract 733,361,573
Example : 1089000000—733,361,573 = 355638427
Magic code
Under each of the digits in your answer, write the letter which corresponds to it using the following table:
0—Y
1—M
2—P
3—L
4—R
5—O
6—F
7—A
8—I
9—B
Example : 3 5 5 6 3 8 4 2 7
L O O F L I R P A
Now read your message backward.
2. Birthday Math
Find a calculator or a pencil and paper.
Ask your friend or eveyone to write down his birthday.
Example : September 28, 1986
Ask your friend (or everyone in the room) to write down the number of the month he/she/was born.
Example : 9 (born in September)
Multiply the month by 4
9 x 4 = 36
Add 13
36 + 13 = 49
Multiply by 25
49 x 25 = 1225
Subtract 200
1225—200 = 1025
Add the day of the month he/she/was born
1025 + 28 = 1053
Multiply by 2
1053 x 2 = 2106
Subtract 40
2106—40 = 2066
Multiply by 50
2066 x 50 = 103300
Add the last two digits of the year of your birth (1986)
103300 + 86 = 103386
Ask your friend to give you his result
103386
Now you can magically tell him his birth date.
Here’s how to do it:
Subtract 10500 from his result
103386—10500 = 92886
9 = month of September
28 = day of birth
86 = year of birth
You may now apply for your soothsayer’s licence!
3. Card Multiplication
Remove Jokers, Kings, Queens, Jacks, Tens
Ask the participant to shuffle the remaining cards.
Fan the cards, instruct the participant to pick a card, memorize it and then put it back into the deck.
Turn your back to the participant.
Ask him to complete the following steps:
Their card x 2
Add 5
Multiply by 5
The participant must remember this number.
Ask the participant to choose another card from the deck.
Add this card to the preceding total.
Ask him to reveal this total now.
You must mentally subtract 25 from his answer.
The two digits are the two cards he had selected.
4. Hate 8
Find a calculator.
Ask your friend to choose a number between 1 and 9 but he is not allowed to choose the number 8.
Example : 7
Multiply the number by 9
7 x 9 = 63
Multiply the answer by 12345679 (no 8)
63 x 12345679 = magic!
Try another number.
6. Age And Address Mathematical Trick
Write the number of your house address.
Example : 121
Multiply this number by 2.
Example : 121 x 2 = 242
Add 5
Example : 242 + 5 = 247
Multiply this number by 50.
Example : 247 x 50 = 12350
Add your age.
Example : 12350 + 27 = 12377
Add 365.
Example : 12377 + 365 = 12742
Subtract 615.
Example : 12742—615 = 12127
Magic:
The first number(s) is/are your house number(s) and the last two numbers are your age.
6. Always Hundred
Find a friend, paper, pencil or calculator.
Choose any number
Example : 69
Add 20.
69 + 20 = 99
Add 50.
99 + 50 = 149
Subtract 10.
149—10 = 139
Add 100.
139 + 100 = 249
Add 20.
249 + 20 = 259
Subtract 80.
249—80 = 169
Subtract your original number.
169—69 = 100
The answer will always be one hundred.
Go out and impress someone!
7. Pick A Number
Pick a number between 2 and 9.
Example : 7
Multiply this number by 2.
Example : 7 x 2 = 14
Add 5.
Example : 14 + 5 = 19
Multiply this number by 50.
Example : 19 x 50 = 950
If you already had your birthday this year, add 1761.
Example : 950 + 1761 = 2711
If you have not yet celebrated your birthday this year, add 1760.
Example : 950 + 1760 = 2710
Subtract your year of birth.
Example : 2711—1987 = 724
Magic:
The first number is the number you picked and the last two numbers are your age.
8. Seventy-Three
Find a piece of paper, a pencil, a calculator and a friend.
Write 73 on a piece of paper, fold it up and hand it to your unsuspecting friend.
Ask your friend to select a four-digit number and enter it twice into a calculator.
Example : 23452345
Ask your friend to divide this number by 137.
Example : 23452345 / 137 = 171185
Now ask your friend to divide the answer by his original four-digit number.
Example : 171185 / 2345 = 73
Ask your friend to look at the folded piece of paper.
You are a maths magician!
Why this happens :
Entering a four-digit number twice (23452345) is equivalent to multiplying it by 10001.(2345 x 10001 = 23452345).
Since 10001 = 73 x 137, the eight-digit number will be divisible by 73, 137, and the original four-digit number.
9. Two To Trick
Find a friend, paper, pencil or calculator.
Choose any number.
Example : 31
Add 5.
31 + 5 = 36
Multiply by 3.
36 x 3 = 108
Subtract 9.
108—9 = 99
Divide by 3.
99 / 3 = 33
Subtract your original number.
33—31 = two will always be the answer.
10. More Two Too
Choose any number.
Example : 73
Add 3.
73 + 3 = 76
Multiply by 2.
76 x 2 = 152
Add your orignal number.
152 + 73 = 225
Divide by 3.
225 / 3 = 75
Subtract your original number.
75—73 = two too
11. Always 5
Find a calculator or a pencil and paper.
Ask your friend (or everyone in the room) to choose any number.
Example : 43
Add the next highest number to it.
43 + 44 = 87
Add 9.
87 + 9 = 96
Divide by 2.
96 / 2 = 48
Subtract your original number.
48—43 = 5
Everyone’s answer will always be 5.
Try another number.
12. More Always Five
Choose any number between 1 and 99.
Example : 22
Multiply this number by 5.
22 x 5 = 110
Add 25 to your product.
110 + 25 = 135
Divide this number by 5.
135 / 5 = 27
Subtract your original number.
27—22 = 5
Everyone’s answer will always be 5.
13. Book Math Trick
Find a book, a pen, a piece of paper and a calculator.
Hand them to your friend.
Ask a friend to choose any page in the book.
Ask your friend to write down the page number on a piece of paper.
Example : He chose page 141.
Now ask your friend to choose one of the first nine lines on that page.
Ask your friend to write down the line number that has been chosen.
Example : He chose line 7.
Ask you friend to choose one of the first nine words on that line.
Ask your friend to write down the number of the word chosen.
Example : He chose word 3.
Close the book.
Hand your friend a calculator and ask your friend to follow these seven steps:
Multiply the page number by 2.
Example: 141 x 2 = 282
Multiply the answer by 5.
282 x 5 = 1410
Add 20.
1410 + 20 = 1430
Add the line number.
1430 + 7 = 1437
Add 5.
1437 + 5 = 1442
Multiply the answer by 10.
1442 x 10 = 14420
Add the word number.
14420 + 3 = 14423
Now ask your friend to tell you the answer.
You must now subtract 250 from that number.
14423—250 = 14173
The last number (3) will tell you the number of the word that your friend picked.
The second to last number (7) will indicate the line number.
The remaining numbers (141) will indicate the page number.
Take the book, turn to that page, find the line and the word on that line.
Magic!
14. Calendar Trick
Ask what day, month and year the person was born.
Then tell him which day of the week this person was born.
How to predict the day :
Example :
Let us assume the person reveals that his date of birth was February 12, 1978.
Two formulas are used for prediction :
January, October = 0
May = 1
August = 2
February, March, November = 3
June = 4
September, December = 5
April, July = 6
Sunday = 0
Monday = 1
Tuesday = 2
Wednesday = 3
Thursday = 4
Friday = 5
Saturday = 6
1—Drop the “19” in the year of birth (1978 becomes 78)
2- Divide this number by 4 and drop the remainder (78 / 4 = 19 remains 2)
3- Add this answer to the year of birth ( 19 + 78 = 97)
4- Add the day of the month of birth to this total (97 + 12 = 109)
5- From the first formula, add the value of the month (February = 3, 109 + 3 = 112)
6- Divide this total by 7 (112 / 7 = 16 remains 0)
7- Take this remainder (0) and apply this number to the days in formula 2) 0 = Sunday
Therefore, he was born on a Sunday.
Go and amaze someone!
15. Four More
Find a friend, paper, pencil or calculator.
Choose any single-digit number
Example : 9
Multiply it by 3.
9 x 3 = 27
Add 12.
27 + 12 = 39
Multiply by 15.
39 x 15 = 585
Divide by 9.
585 / 9 = 65
Multiply by 2.
65 x 2 = 130
Divide by 10.
130 / 10 = 13
Subtract your original number.
13—9 = 4
The answer will always be four.
Go out and impress someone!
16. Missing Number
Without looking at your friend, ask him/her to write down any number that is at least four digits long.
Example : 13579
Then ask your friend to add up the digits.
1+3+5+7+9 = 25
Now subtract this answer (25) from the first number.
13579—25 = 13554
Ask your friend to cross out one digit from the answer. (You cannot cross out a zero)
1X554
Now ask our friend to read out slowly the digits that are left.
1554
You now magically say : “The missing number is three.”
How to do the missing number maths trick
This is a power of 9 trick.
Once your friend has crossed out a digit and reads out the digits that are left, you simply add them up.
Example : 1+5+5+4 = 15
You now add on to your answer to get the next number that divides by nine!
The next number to divide by 9 after 15 is 18.
Therefore, you need to add on three.
This is the number that was crossed out!
17. Love 23
Find a calculator.
Ask your friend (or everyone in the room) to choose any number
Example : 37
Add 25.
37 + 25 = 62
Multiply the answer by 2.
62 x 2 = 124
Subtract 4.
124—4 = 120
Divide by 2.
120 / 2 = 60
Subtract your original number.
60—37 = Love that number!
Try another number. The answer will always be 23.
18. Amazing 9
Every student writes down his telephone number (without area code) or any number of as many digits.
Now shuffle these digits around to make a smaller number.
Example : 6358 can be shuffled to make 3865.
The more digits in his number, the better!
Now subtract the small number from the big number and tell him to keep the answer to himself.
Now highlight any digit (not a 0) in his answer.
Add up all the other digits:
3 4 1 6 2 2 9 => 3+1+6+2+2+9 = 23
Now go around the class, asking for the final answers and IMMEDIATELY tell the pupils which number they highlighted :
Answer = “23”
“You highlighted “4”
Method
One of the most incredible properties of our number system is its power to make tricky calculations very easy.
Since we write our numbers in base 10, it follows that when we subtract the digits from a number we always end up with a multiple of 9.
(This is basically saying that 1000—1 and 100—1 and 10—1 are all multiples of 9.)
One of the properties of any multiple of 9 is that its digital root (the sum of its digits, with the addition repeated until a single digit is reached) is also 9.
Putting these two together we can see that the answer to the subtraction is always going to be a multiple of nine.
All you have to do is answer back with the smallest number that will make his total up to a multiple of 9.
If it is already a multiple of 9, then he must have crossed out 0 or 9, but zero was forbidden; therefore 9 is the answer.
19. Recurring Number
Write down the following 8-digit number on a piece of paper: 1 2 3 4 5 6 7 9
Ask a participant to circle one of the digits.
Example : The participant circles number 7.
Now ask the participant to multiply the 8-digit number by 63.
A magic result happens :
1 2 3 4 5 6 7 9 x 6 3 = 7 7 7 7 7 7 7 7 7
The answer is a row of the chosen number 7.
How to do this maths trick:
When the participant circles a number, you need to multiply the chosen number by 9.
Example: If 3 was chosen you would multiply 3 x 9 = 27.
Then you would ask the participant to multiply the 8-digit number by the number you obtained (27)
Therefore, multiply 12345679 by 27 and you magically get the answer 333333333.
Einstein would be proud!
20. Roll Them
Find a calculator, two dice and a friend.
Ask your friend to roll the dice without revealing to you the numbers.
Example : Your friend rolls a 4 and a 6.
Ask your friend to multiply the number on the first die by 2.
4 x 2 = 8
Add 5.
8 + 5 = 13
Multiply by 5.
13 x 5 = 65
Add the number on the second die.
65 + 6 = 71
You can now predict the numbers on the two dice.
Here is what you must do:
Subtract 25
71—25 = 46
4 = first die
6 = second die
Go and buy yourself a swami hat!
21. Seven And Thirteen
Find a calculator and a friend.
Ask a friend to select a three-digit number and enter it twice into the calculator.
Example : 345345
Ask your friend to divide this number by 11.
Example : 345345 / 11 = 31395
Now, ask you friend to divide the result by 13.
Example : 31395 / 13 = 2415
Ask your friend to divide this answer by the original three-digit number.
Example : 2415 / 345 = 7
Now, magically tell your friend that the answer is 7.
To change the final answer to 13, tell your friend to divide by 7 in step 3.
Example : 31395 / 7 = 4485
4485 / 345 = 13
Why this happens :
Entering a three-digit number twice (345345) is equivalent to multiplying it by 1001. (345 x 1001 = 345,345).
Since 1001 = 7 x 11 x 13, the six-digit number will be divisible by 7, 11, 13.
