The age from phone number
To tell the age of anyone, ask him to write down last four digits of a telephone number. Suppose the four digits are 8231. Let him conceive a new four digit number by placing the above digits in a new order, say 2318. Now, subtract the smaller number from the bigger one. In this case the result is 5913.
Add all the digits i.e. 5 + 9 + 1 + 3 = 18 = 1 + 8 = 9
Add sixteen to the result i.e. 9 + 16 = 25
Now ask the person to add this number to his birth year. i.e. 1945 + 25 = 1970
Now ask him about the final result. You can tell his birth year by subtracting 25 from the final result i.e. 1970 – 25 = 1945
 The age of anybody
If someone is acquainted with the basics of arithmatic, he can tell the age of anybody by following the simple method given below:
[Step 1] – Tell him / her to add his / her present age and the next year’s age.
[Step 2] – Tell him / her to multiply the sum by 5.
[Step 3] – Tell him / her to add the unit digit of the year in which he / she was born.
[Step 4] – Tell him / her to subtract 5 from the final result.
[Step 5] – The left two digits will indicate his / her age.
Suppose today your friend is 12 years old and he was born in 1976.
[Step 1] – Present age + next year’s age = 25
[Step 2] – Step 1 x 5 i.e. 25 x 5 = 125
[Step 3] – Step 2 + unit digit of the year in which your friend was born i.e. 125 + 6 = 131
[Step 4] – Step 3 – 5 = 131 – 5 = 126
[Step 5] – The left two digits are 12, hence his age.
 Number of currency notes in one’s pocket.
[Step 1] : Ask him to write down the number of currency notes in his pocket.
[Step 2] : Then double it.
[Step 3] : Add 1 to the above number.
[Step 4] : Multiply above number by 5.
[Step 5] : Now add 5 to the above result.
[Step 6] : Next ask him to multiply the result by 10.
[Step 7] : Subtract 100 from the above number.
[Step 8] : Now ask him to tell you the number. Delete the last two digits from this number and you will get the number of the currency notes eventually.
Suppose your friend writes down the number of currency notes as: 16
On doubling it becomes : 32
Then he adds 1 to the above number : 33
He multiplies the above number by 5 : 165
He adds 5 to the above result : 170
Next he multiplies the number by 10 to get : 1700
He then subtracts 100 from the above number to get : 1600
Now ask him to tell you the number after deleting the last two digits from the result (i.e. 1600), you can tell that he has 16 currency notes in his pocket.