Average age of 25 boys of a class is 18 years. When the age of class teacher is included the average age become 20 years . Find the age of the class teacher
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25 -------18
26--------20
increase =20 -18 =2
25×2 =50
so 20 +50 =70 yrs old teacher
26--------20
increase =20 -18 =2
25×2 =50
so 20 +50 =70 yrs old teacher
mathupto12:
your way suits for upper level entrance type question
Answered by
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Average age of 25 boys=18
Sum of their ages=18x25=450
Let the age of teacher be x
So now sum of the ages is=450+x
Total no of persons are26
Average of all =20
(450+x)/26=20
+x=520
x=520-450
=70yrs
Sum of their ages=18x25=450
Let the age of teacher be x
So now sum of the ages is=450+x
Total no of persons are26
Average of all =20
(450+x)/26=20
+x=520
x=520-450
=70yrs
i had fix it
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