standard_description: Apply and extend previous understandings of addition and subtraction to add and subtract rational numbers; represent addition and subtraction on a horizontal or vertical number line diagram.
problem_activity: Task
There are 270 students at Colfax Middle School, where the ratio of
boys to girls is 5:4. There are 180 students at Winthrop Middle
School, where the ratio of boys to girls is 4:5. The two schools
hold a dance and all students from both schools attend.  What
fraction of the students at the dance are girls?


aligns: no