What does the sum of all the numerals from the numbers from $100$ up to $1000$ equal to?

Question

What does the sum of all the numerals from the numbers from $100$ up to $1000$ equal to?

Answer 1

You can answer this by using the following formula:

$\sum^n_{i=1}i=\dfrac{n(n+1)}{2}$

The proof of which can be found here. If we rephrase your question in mathematical terms, using this sum notation, you are asking:

$\sum^{1000}_{i=100}i=?$

This is equal to

$\sum^{1000}_{i=1}i-\sum^{99}_{i=1}i$

So use the formula above with these values to get the answer.