1. The mean of 30 observations was 25. It was found later that an observation 50 was wrongly taken as 20. The corrected mean is:
Solution:
Corrected mean= (25*30 – 20+50)/30
= 750+30/30
= 780/30
= 26.
2. The average age of 10 students in a class is 10 years. Out of these, the average age of 6 students is 11 years and that of the other 3 students is 9 years. The age of the 10th student is:
Solution:
The age of the 10th student = 10*10 - [11*6 + 9*3]
= 100 – [66+27]
= 100-93
= 7.
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