How do you calculate 1+2+3+4+5+6+7+8+9+10 quickly?

You can calculate the sum of $1 + 2 + 3 + \dots + 10$ quickly using a well-known formula for the sum of an arithmetic series. The formula is:

$$\text{Sum} = \frac{n(n+1)}{2}$$

where $n$ is the largest number in the series. In this case, $n = 10$.

Plugging in the value of $n$:

$$\text{Sum} = \frac{10(10+1)}{2} = \frac{10 \times 11}{2} = \frac{110}{2} = 55$$

So, the sum of $1 + 2 + 3 + \dots + 10$ is 55.

Quick Explanation:

This formula works because the sum of the first and last number is the same as the sum of the second and second-to-last number, and so on. For example:

$$(1 + 10), (2 + 9), (3 + 8), \dots = 11, 11, 11, \dots$$

There are 5 such pairs, so the total sum is $5 \times 11 = 55$.

Source: Some or all of the content was generated using an AI language model