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

Question : 1

In a class there are 30 boys and their average age is 17 years. On one boy aged 18 years leaving the class and another joining, the average age becomes 16.9 years. The age of new boy is

a) 11 years

b) 25 years

c) 15 years

d) 13 years

Question : 2

The average age of 20 boys in a class is 12 years. 5 new boys are admitted to the class whose average age is 7 years. The average age of the boys in the class becomes

a) 9.5 years

b) 8.2 years

c) 11 years

d) 12.5 years

Question : 3

The average age of 14 girls and their teacher’s age is 15 years. If the teacher’s age is excluded, the average reduces by 1. What is the teacher’s age?

a) 32 years

b) 35 years

c) 29 years

d) 30 years

Question : 4

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 : 5

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 : 6

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