The average age of 30 students in a class is 10. When teachers age is added the average age becomes 11. Find out the age of the teacher? VERY SIMPLE METHOD – USE YOUR COMMONSENSE: Let us assume that the teachers age was also 10. In such case the average of all 31 people ( 30 students + 1 teacher) remains same which is 10. But this is not the case. On arrival of teacher the average has increased by 1. So 1 has been added to all the 31 people of the class. It means teachers age should be more than 10. How much more ? It is 31 more … 10 + 31 = 41 FORMULA METHOD TEACHERS AGE = NEW AVERAGE + (NUMBER OF STUDENTS X DIFFERENCE OF AVERAGES) In above case TEACHERS AGE = 11 + ( 30 X 1) = 11+ 30 = 41 GENERAL FORMULA NEW PERSON’S AGE OR WEIGHT = NEW AVERAGE + ( NUMBER OF PEOPLE BEFORE NEW PERSON CAME X DIFFERENCE BETWEEN THE NEW AND OLD AVERAGES)
Posted on: Tue, 03 Sep 2013 05:34:12 +0000
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