The average of seven numbers is 18. The average of first three numbers is 14 and the average of last three numbers is 19. What is the middle number

The average age of a class of 32 students is 16 yrs. If the teacher's age is also included, the average increases by one year. Find the age of the teacher.

In a class, the average age of 30 boys is 13 years and the average of 20 girls is 12 years. What is the average age of the whole class

What is the average of first 21 multiples of 7