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

Question : 1

The average age of 30 boys in a class is 15 years. One boy, aged 20 years, left the class, but two new boys came in his place whose age differ by 5 years. If the average age of all the boys now in the class becomes 15 years, the age of the younger newcomer is :

a) 15 years

b) 20 years

c) 8 years

d) 10 years

Question : 2

The average age of a family of 10 members is 20 years. If the age of the youngest member of the family is 10 years, then the average age of the members of the family just before the birth of the youngest member was approximately

a) 12.5 years

b) 27.14 years

c) 11$1/9$ years

d) 14.28 years

Question : 3

From a class of 42 boys, a boy aged 10 years goes away and in his place, a new boy is admitted. If on account of this change, the average age of the boys in that class increases by 2 months, the age of the newcomer is :

a) 17 years

b) 19 years

c) 12 years 2 months

d) 10 years 6 months

Question : 4

The average age of group of 20 girls is 15 years and that of another group of 25 boys it is 24 years. The average age of the two groups mixed together is

a) 20 years

b) 19.5 years

c) 21.5 years

d) 21 years

Question : 5

Average age of 8 men is increased by 3 years when two of them whose age are 30 and 34 years are replaced by 2 persons. What is the average age of the 2 persons ?

a) 32 years

b) 24 years

c) 48 years

d) 44 years

Question : 6

There were 24 students in a class. One of them, who was 18 years old, left the class and his place was filled up by a newcomer. If the average of the class thereby, was lowered by one month, the age of the newcomer is

a) 15 years

b) 14 years

c) 17 years

d) 16 years