How do I work out the sum of all numbers from 1 to 100 without a calculator?
If you know the formula for the sum of the first n natural number:1 + 2 +u2026+ n = 1/2 *n *(n +1), you will get to:1 + 2 + u2026+ 100 = 1/2 *100*(101)From here, you can easily get the answer by dividing 101 by 2 (equivalent to multiplying it by 1/2) to get 50.5.Then multiply this 100 by moving the decimal point in 50.5 two places to the right. (50.5 becomes 505.0 when the decimal is moved 1 place to the right, which is equivalent to multiplying by 10. It becomes 5050.0 when the decimal is moved 2 places to the right, which is equivalent to multiplying it by 100).You can drop the u201c.0 u201c in your final answer.Final answer: The sum of all natural numbers from 1 to 100 = 5050.*** NO CALCULATOR REQUIRED! ***Good luck!