## Find one’s complement of a decimal number.

One’s complement of a binary number (1001_{2}) is (0110_{2}). That is, we simply flip the bits. This is easy to do in binary. However, if the number is in base 10, then do we do that. Convert that to base 2 then flip the bits and change it back to base 2? Maybe, but if […]

## Digit Math Application: Proving that all numbers ending with 5 are divisible by 5

Please read Digit Math: Introduction before you continue. The problem It seems I have developed a fascination for the number 5, so here we go again. Here I would be using Digit Math to prove that all integers  which end with digit 5 are always divisible by 5. The proof Case 1: Take a two […]

## Digit Math Application: Proving the correctness of shortcut method to squaring numbers ending with 5

Please read Digit Math: Introduction before you continue. The problem Someday, somewhere I came to know that any number which ends with the digit 5 can be easily squared. The trick can be easily demonstrate using an example. Suppose we want to find the square of 25. Trick is to take the number before 5 […]

## Digit Math Application: Proving that multiplying with 10**n puts n zeros at the end

Please read Digit Math: Introduction before you continue. The problem This is a very fundamental concept that we were taught when we were in junior schools. Now, think of it, what it says. If you add $$x$$ ten times then you will get $$x\omega0$$. If you add $$x$$ hundred times then you will get $$x\omega00$$; and so […]

## Digit Math: Introduction

The person in the above image is Bertrand Russell. Famous Mathematician and Logician.  An excellent graphic novel, Logicomix, is based around his life. That is a must read. First thing first. Even if you are not a Math demi-god, it is fine, Digit Math is still for you. In fact my academic track record shows that I […]

## Amar’s blog: Making sense of standard deviation

Amar’s blog: Making sense of standard deviation. Very good blog post which tries to explain the intuitive meaning of Standard Deviation.