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The average of n observations is 40. If one observation of value 80 is added, then the average of all the observations is 41. What is the value of n?

The average of n observations is 40. If one observation of value 80 is added, then the average of all the observations is 41. What is the value of n? Correct Answer 39

Average of n observations = 4

Sum of n observation = 40n

Average of (n + 1) observation = 41

Sum of (n + 1) observation = (41) × (n + 1)

According to the question

40n + 80 = 41(n + 1)

40n + 80 = 41n + 41

41n – 40n = 80 – 41

n = 39

So, number of observation be 39

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