M. Tyra Solutions for Chapter: Average, Exercise 1: Exercises

In a yoga class there were $12$ members. Two members left the class and $4$ new members joined. If the average age decreased by $4$ years and the total age decreased by $2$ years, what is the new average age of the class? (in years)

A professional institute's total expenditure on students for a particular course is partly fixed and partly varies linearly with the number of students. The average expense per student is $₹615$ when there are $24$ students and $₹465$ when there are $40$ students. What is the average expense when there are $60$ students?

The average weight of boys in a class is $45 \mathrm{kg}$ while that of girls is $36 \mathrm{kg}$. The average weight of the whole class is $42.25 \mathrm{kg}$. What is the respective ratio between the number of boys and girls in the class?

$15$ years ago the average age of a family of four members was $40$ years. Two children were born in this span of $15$ years. The present average age of the family remains unchanged. Among the two children who were born during the $15$ years, if the older child at present is $8$ years older than the younger one, what is the ratio of the present age of the older child to the present age of the younger child?

In a primary school the average weight of male students is $65.9 \mathrm{kg}$ and the average weight of female students is $57 \mathrm{kg}$. If the average weight of all the students (both male and female) is $60.3 \mathrm{kg}$ and the number of male students in the school is $66$, what is the number of female students in the school?

A batsman played three matches in a tournament. The ratio of the score of $1\mathrm{st}$ to $2\mathrm{nd}$ match was $8 : 9$ and that of the score of $2\mathrm{nd}$ to $3\mathrm{rd}$ match was $3 : 2$. The difference between the $1\mathrm{st}$ and the $3\mathrm{rd}$ match was $16$ runs. What was the batsman's average score in all the three matches?

Three Science classes A, B and C take a Life Science test. The average score of students of class A is $83$. The average score of students of class B is $76$. The average score of class C is $85$. The average score of class A and B is $79$ and the average score of class B and C is $81$. Then the average score of classes A, B and C is

The average weight of boys in a class of students is $58 \mathrm{kg}$, while that of girls is $50 \mathrm{kg}$. The average weight of the entire class is $53 \mathrm{kg}$. The number of girls is approximately what per cent of the number of boys in the class?