Multiple choice general knowledge math & puzzles

Can you find a quick and elegant way to add the numbers from 1 to 26 ? In other words, what is the sum you obtain in the following case: 1 + 2 + 3 + ....... + 26 =

  1. 340

  2. 256

  3. 500

  4. 351

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Use the arithmetic series sum formula: n(n+1)/2. For n=26: 26(27)/2 = 351. This elegant formula (attributed to Gauss) pairs numbers from opposite ends: (1+26)+(2+25)+... = 27, with 13 such pairs. 27 × 13 = 351.