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Q.

The average of five numbers is thirty. When one number is removed, the mean becomes 28. What is the number that is not included?


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a

30

b

40

c

38

d

39 

answer is C.

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Detailed Solution

Given, The average of five numbers is thirty. When one number is removed, the mean becomes 28.
Let x represent the excluded number and a represent the sum of the other four numbers.
We know that mean = Sum of all observationsNumber of observations.
x + a5 = 30
x + a = 150……(1)
Also, a4 = 28.
a = 112
Substitute a = 112 in (1).
x + 112 = 150
x = 150 - 112 = 38
Hence, the excluded number is 38.
So, option 3 is correct.
 
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