Question

Sum the digit in between 1 to 405

Answer 1

Answer:

82,215

Step-by-step explanation:

To get the answer above, you could add up all the digits like 1+2+3... +405, but there is a much easier way to do it! Use the following formula:

n(n + 1)/2 = Sum of Integers

In this case, n=405, thus you get your answer by entering 405 in the formula like this:

405(405 + 1)/2 = 82,215