Find missing Row in Excel || Math Interview Puzzles

Math interview puzzles are problems or challenges that are often used by employers as part of a job interview process to assess a candidate's problem-solving, critical thinking, and mathematical skills. Math interview puzzles are important because they provide a way for employers to assess a candidate's problem-solving and critical thinking skills, as well as their ability to apply mathematical concepts in real-world scenarios.

Puzzle Details: We are given a series of numbers that contains integers from 1 to 50, including both 1 and 50. However, the numbers are in a jumbled form, which means that they are not arranged in increasing or decreasing order. and there is 1 integer missing. You have to identify the missing integer logically. 


We know that the sum of all the numbers from 1 to n can be calculated by using the formula  (n*(n+1)/2) where n is the last number in the series. remember this formula is applicable only to positive natural numbers.

let's understand this equation with a simple example, let's consider a series with 5 numbers 1 2 3 4 5. we can use the equation to find the sum of these numbers. here the last number in the series is 5 hence n is 5. hence this will result in 5*(5+1)/2 = 15.

similarly, we will try for 50 numbers and hence n becomes 50. Therefore, the sum of all the numbers from 1 to 50 is

50*(50+1)/2  (Here, n = 50)

  = 50*(51)/2

  = 25*51

  = 1275

hence the sum of all numbers from 1 to 50 is 1275.

Therefore, all we need to do is to sum all the integers present in the given series and subtract the sum from 1275. The difference between 1275 and the sum which is obtained would give us the missing integer. Because 1275 is the sum of the natural numbers from 1 to 50 and the number obtained is the sum of the natural numbers from 1 to 50 without including the missing number. hence subtracting the sum of the given series from 1275 will fetch the missing number.

consider the series with the number 28 is missing and hence the sum of the given natural numbers will yield 1247. Subtracting the sum from 1275 will fetch 28 and that will be the answer. This is the logic to be used to find the missing number in the given series provided that the series is positive natural numbers. 

Watch the video for a detailed explanation

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