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Aptitude Day 172

Problems on Average:

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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