Level 2
There are 4 girls and 5 boys.
The average height of the 4 girls is 155 cm.
The average height of 5 boys is 164 cm.
What is the average height of all the children?
Level 3
There are 4 girls and some boys.
The total height of the children is 1440 cm.
The average height of the 4 girls is 155 cm.
The average height of the boys is 164cm.
How many boys are there?