The average age of a class is 20 years.including the teacher whose age is 54 years, the average will be 21 years. what is the number of students in the class?
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let the sum of ages of stud. be x
and no. stud. be y
x/y = 20, so x = 20y
then
x+54/y+1 = 21
x+54=21y+21
33=21y-x
33= 21y - 20y
33 = y
and no. stud. be y
x/y = 20, so x = 20y
then
x+54/y+1 = 21
x+54=21y+21
33=21y-x
33= 21y - 20y
33 = y
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