4 DEC SS Q.21

21Out of a total of 10 students, the average weight of 9 students is 60 kg. If the Weight of the 10 student is 9 kg more than the average weight of all the 10 students, then the weight of 10 student would be :

Option : C
Explanation : Let weight of 1Oth student = x kg
Average weight of 9 students = 60 kg
total weight of 9 students = 9 x 60 = 540 kg
Now, Average weight of 10 students
= (540 + x)/10
According to the question,
x - (540 + x)/10 = 9
1Ox - 540 - x = 90
9x = 90 + 540 = 630
x = 630/9 = 70 kg

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