Multiple choice general knowledge math & puzzles

While adding the first few continuous natural numbers, a candidate missed one of the numbers and wrote the answer as 177. What was the number missed ?

  1. 11

  2. 12

  3. 13

  4. 14

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

The sum of first n natural numbers is n(n+1)/2. We need this close to 177. Testing values: 18×19/2 = 171 (too low), 19×20/2 = 190 (too high). The student got 177, so they were adding 1-19 but missed a number. 190 - 177 = 13, which is the missed number. The correct sum of 1-19 is 190.