Triangle ABC is similar to triangle A'B'C'. The coordinates of triangle ABC are shown in the diagram. The perimeter of triangle A'B'C' is 15 units. A dilation, center at the origin, was used to create these triangles. What was the scale factor used for the dilation?

Randy and trey take turns cleaning offices on the weekends. it takes randy at most 4 hours to clean the offices. it takes trey at most 6 hours to clean the offices. what is the greatest amount of time it would take them to clean the offices together? 2.4 hours 2.5 hours