3. The arithmetic mean of 12 observations is 7.5. If the arithmetic mean of 7 of these observations
is 6.5, the mean of the remaining observations is
(a) 5.5
(b) 8.5
(c) 8.9
(d) 9.2
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Answer:
Total sum of 12 obs = 12*7.5 = 90
Total sum of first 7obs = 7*6.5 = 45.5
Sum of remaining numbers = 90-46 = 44.5
Mean = 44.5/5 = 8.9
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