Question:
The mean of 25 observations is 36. If the mean of the first 13 observations is 32 and that of the last 13 observations is 40, then the 13th observation is ________.
The mean of 25 observations is 36. If the mean of the first 13 observations is 32 and that of the last 13 observations is 40, then the 13th observation is ________.
Options:
- 36
- 30
- 24
- 28
- 36
- 30
- 24
- 28
Correct Answer: a)
Explanation:
‘
i Mean of first 13 obser√ations = 32
.. Sum of first 13 obser√ations =32 x 13=416 1
‘ Mean of last 13 obser√ations = 40
i .*. Sum of last 13 obser√ations = 40 x 13 = 520
Now, mean of 25 obser√ations = 36
hon a
‘ .. Sum of 25 obser√ations = 36 x 25 = 900 ‘
‘ ..13th obser√ation = (416 + 520 – 900) = 36.
‘
i Mean of first 13 obser√ations = 32
.. Sum of first 13 obser√ations =32 x 13=416 1
‘ Mean of last 13 obser√ations = 40
i .*. Sum of last 13 obser√ations = 40 x 13 = 520
Now, mean of 25 obser√ations = 36
hon a
‘ .. Sum of 25 obser√ations = 36 x 25 = 900 ‘
‘ ..13th obser√ation = (416 + 520 – 900) = 36.