model 7 average on ages/weight Section-Wise Topic Notes With Detailed Explanation And Example Questions

Question : 1

In a school with 600 students, the average age of the boys is 12 years and that of the girls is 11 years. If the average age of the school is 11 years and 9 months, then the number of girls in the school is

a) 150

b) 450

c) 350

d) 250

Question : 2

The average age of 45 persons is decreased by $1/9$ year when one of them of 60 years is replaced by a new comer. Then the age of the new comer is :

a) 55 years

b) 45 years

c) 49 years

d) 59 years

Question : 3

From a class of 24 boys, a boy, aged 10 years, leaves the class and in his place a new boy is admitted. As a result, the average age of the class is increased by 2 months. What is the age of the new boy ?

a) 15 years

b) 12 years

c) 13 years

d) 14 years

Question : 4

In a family of 5 members, the average age at present is 33 years. The youngest member is 9 years old. The average age of the family just before the birth of the youngest member was

a) 29 years

b) 30 years

c) 24 years

d) 25 years

Question : 5

The average age of 8 men is increased by 2 years when two of them whose age are 21 and 23 years replaced by two new men. The average age of the two new men is

a) 24 years

b) 22 years

c) 30 years

d) 28 years

Question : 6

In a family, the average age of a father and a mother is 35 years. The average age of the father, mother and their only son is 27 years. What is the age of the son ?

a) 11 years

b) 12 years

c) 10 years

d) 10.5 years