Solve:

1.
Jim is 12 years old. His sister is twice younger. His mother is 3 times older than Jim. Jim's father is 6 years older than Jim's mother. How old are Jim's sister, mother and father?

What is their average age?

3.
What is the average number of students in each class if there are 250 students in 10 classes?

2.
One of the two movies has a length of 2 hours and 15 minutes.
The average length of the two movies is 1 hour and 45 minutes.
What is the length of the second movie?

Hint: 1 hour has 60 minutes.

4.
The height of three basketball players is 210 cm, 220 cm and 191 cm.
What is their average height?