The average age of a class of 40 students and a teacher reduces by 0.5 years, if we exclude the teacher. If the initial average age is 18 years, then what is the age of the teacher?

If double the age of the daughter is added to the age of her mother, the sum is 70 and if double the age of mother is added to the age of the daughter, the sum is 95. The respective ages of daughter and mother (in years) are:

Ramiya got married 8 years ago. Her present age is 6/5 times her age at the time of her marriage. Ramiya’s brother was 10 years younger than her at the time of her marriage. What is the ratio of Ramiya’s present age and her brother’s age at the time of her marriage?

Average age of x students in a group is 20. When 4 new students are admitted with a age of 7.5 years each, then the average is decreased by 5. What is the value of x?

In a class, there are certain numbers of students. Their average age is 12 years. If two students leave the class, their ages are 23 years and 25 years respectively. Then the average age of the class becomes 11 years. Find the number of students in the class.

10 years ago, respective ratio of the age of mother and daughter was 4 : 1. 10 years later, the respective ratio of the age of mother and daughter will become 2 : 1. At present, what is the sum of their age?

Five years ago the sum of the ages of A and B was 58 years. The difference between B's age 8 years ago and A's age 8 years hence is 16 years. The ratio of the present ages of A and B is:

In a school, $${3\over 8}$$ of the number of students are girls and the rest are boys. One-third of the number of boys are below 10 years and $${2\over 3}$$ of the number of girls are also below 10 years. If the number of students of age 10 or more years is 260, then the number of boys in the school is: