The ratio of teachers to students at washington middle school is 1: 15. if 900 students attend the middle school, how many teachers are there?

teachers

Some boys and girls were asked if they had a pet. one third of the group were boys. there were 20 boys. 20% of the girls had a pet. boys with a pet : girls with a pet = 1 : 5 i need to know how many girls there are.

The lengths of all sides of a triangle are integers when measured in decimeters. one of the sides has length of 1 dm and another of 3 dm. find the perimeter of the triangle.'

Mat bought a phone for $100. he has to pay $30 per mouth. if he has paid $640 in total, how many mouth has he had the phone?