The youth center has another mural painted inside the building. if the original painting is 3 feet by 2 feet, and the mural is 15 feet by 10 feet, what is the scale comparing the painting to the mural? a) 3ft: 10ft b) 1ft: 5ft c) 1ft: 3ft d) 2ft: 15ft

He scale is determined by dividing the respective measures of the two paintings.

Original painting           mural       scale factor
3                                    15            original / mural = 3 / 15 = 1 / 5
2                                    10            original  / mural = 2 / 10 = 1 / 5 
As you see the scale to comparing the original to the mural es   1 feet : 5 feet.   
It  means that the measures of the original painting must be multiplied by 5 to obtain the measures of the mural.