Maths Trick - Guess the number

1. Ask your friend to think of any number between 1 to 10.

    Lets say, s/he had thought of 3. 

2. Ask him/her to double the number.

    6

3. Ask him/her to add 10 to the result (step 2).

    6 + 10 = 16

4. Ask him/her to divide the new number with 2.

    16 / 2 = 8

5. Ask him/her to tell the result and tell them you would tell the number s/he has thought.

    8

Thinking how you would tell him what number s/he has thought. It's very simple, just subtract 5 from the number he has told and you would get the original number he has thought. 

Here it is, 8 - 5 = 3

Simple right! Now want to know how it works, just see the below explanation

In the entire process, you are indirectly adding the original number by 5 and hence by knowing the end result you can guess the original number by just subtracting it by 5

Step 1 - Say the original number what your friend has thought is a.

Step 2 - Double the number - 2a

Step 3 - Add 10 to the new number - 2a + 10

Step 4 - Divide the new number by 2 (2a + 10)/2 = (2a/2) + (10/2) = a + 5

Step 5 - New number - a + 5

Therefore, Original number = New Number - 5 = a + 5 - 5 = a

Note: You can also use 2 and 3 digit numbers to make it harder! 

Have fun playing this trick on your friends.