Mathemagic
Trick 1
Write down any three-digit number
Repeat the number to make a six-digit number
Divide this number by 7
Divide the answer by 11
Divide the answer by 13
Interesting?
Trick 2
Write down a number (eg phone number)
Reverse the order of the digits.
Subtract the smaller number from the larger number.
Find the sum of the digits in the answer.
Repeat summing the answer digits until you have a single digit.
It will be 9
Why is it so?
Trick 3
Circle a number.
Cross out the other numbers in the same row and column.
Repeat this process.
Add up the numbers in the 4 circles.
Why do the circled numbers always add up to 34?
Cross out the other numbers in the same row and column.
Repeat this process.
Add up the numbers in the 4 circles.
Why do the circled numbers always add up to 34?
Trick 4
Write down the last 4 digits of your phone number.
Rearrange these digits in any way you like.
Subtract the smaller number from the larger. Add the digits in the result.
(If this total contains 2 or more digits, continue to add the digits until you have a one digit result)
Add the current year (eg 2018)
Subtract 16 from this result.
Subtract the year you were born
Adding 7 to the final result gives your age.
Rearrange these digits in any way you like.
Subtract the smaller number from the larger. Add the digits in the result.
(If this total contains 2 or more digits, continue to add the digits until you have a one digit result)
Add the current year (eg 2018)
Subtract 16 from this result.
Subtract the year you were born
Adding 7 to the final result gives your age.
Trick 5
Write down any number less than 99 on a piece of paper and conceal it.
Get a student to write down any number between 50 and 100 without you seeing it.
You subtract the number you wrote the piece of paper from 99 and tell the student to add this to their number.
Tell the student to cross off the first digit and add it to the result.
Now tell the student to subtract the result from the original number.
This answer will match the number written on the concealed piece of paper.
Get a student to write down any number between 50 and 100 without you seeing it.
You subtract the number you wrote the piece of paper from 99 and tell the student to add this to their number.
Tell the student to cross off the first digit and add it to the result.
Now tell the student to subtract the result from the original number.
This answer will match the number written on the concealed piece of paper.
Trick 6
Write down any number
Add the next highest number
Add 9 to that result
Divide by 2
Now subtract your original number
The answer is always 5
Why is it so?
Add the next highest number
Add 9 to that result
Divide by 2
Now subtract your original number
The answer is always 5
Why is it so?
Trick 7
Write down any number between 3 and 10.
Add 5 to this number to generate a second number.
Square the first number
Square the second number
Add these two squared numbers together and multiply the result by 2
Given this total you can determine the two numbers originally written down.
Subtract 25 from the result.
Find the square root of this result.
Subtract 5
Divide by 2 and you will have the first number add 5 to this and you will have the second number.
Add 5 to this number to generate a second number.
Square the first number
Square the second number
Add these two squared numbers together and multiply the result by 2
Given this total you can determine the two numbers originally written down.
Subtract 25 from the result.
Find the square root of this result.
Subtract 5
Divide by 2 and you will have the first number add 5 to this and you will have the second number.