Question 141

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?

Solution

The Average of n observation = 40

total of n observation = 40 n

on adding 80, total becomes = 40n + 80 and number of observation = n +1

Now average = 41

so according to question $$\dfrac {40n + 80}{n+1} = 41 $$

$$\Rightarrow 40n + 80 = 41 (n+1)$$

$$\Rightarrow 41n - 40 n = 80-41 $$

$$\Rightarrow n = 39 $$Ans

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