The average age of 6 members of a family is 20 years. If the age of the servant is included, then the average age increase by 25%. What is the age (in years) of the servant?
Average age of family of 6 members = 20 years
=> Total age of the family = $$6\times20=120$$ years
Let the age of servant = $$x$$ years
Average age of family including servant = $$20\times\frac{125}{100}=25$$ years
=> $$\frac{120+x}{7}=25$$
=> $$120+x=25\times7=175$$
=> $$x=175-120=55$$ years
=> Ans - (D)
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