You can find a calendar from everywhere. So you can do a simple magic to amaze your friend with this calendar magic. You can have a paper ,pen and a calculator for this.But all these needs for you friend.
Ask a friend to circle 9 numbers in a calendar which should be a row of 3 by 3.
Ask your friend to calculate all numbers using the pen and piece of paper.He will try to add those with writing all numbers in the paper.
When he do it,
You can tell him that you can add those numbers within a second.
You give the correct answer and have them check it with a calculator.
What is the secret?
you need to multiply the number in the center of the circled numbers by 9.
So According to the picture example,its middle number is 10. So we have to multiply that 10 by 9
So answer is 90.
For make this more easy to you you can use easy method to multiply by 9 .
You can multiply any number by 10 and reduce 9 from it.
Example : If the middle number is 29, 29 *10=290
Answer is 281
So now you can give the calculator to your friend and you can tell “I can add calendar numbers before calculator”
You know the trick and its simple.