A photograph of a painting measures 13 units by 17 units. If the scale factor is \(\frac{1}{3}\), what is the actual size of the painting?
WHAT DO I DO?
We have to assume that the actual painting is larger than the photo.
The area of the photo = 17 x 13 = 221sq units
The area of the actual painting - in square units - will be 221 x [ the scale factor]^2
And the scale factor = 3 so.....
221 x [3]^2 = 221 x 9 = 1989 square units
This makes sense........each dimension of the painting is 3 times that of the same dimension in the photo....so....if the area of the photo = L x W the area of the painting = 3L x 3L = 9[W x L]......9 times as much....!!!!
Treat the starting painting as X
1/3 is the scale factor
Put the orginal on top, in place of 1, and the outcome is the original paintings size
13/3 = 4.3333333333333333
17/3 = 5.6666666666666667
So the painting was originally 4.3 by 5.6 or 5.67 depending on how you round.
We have to assume that the actual painting is larger than the photo.
The area of the photo = 17 x 13 = 221sq units
The area of the actual painting - in square units - will be 221 x [ the scale factor]^2
And the scale factor = 3 so.....
221 x [3]^2 = 221 x 9 = 1989 square units
This makes sense........each dimension of the painting is 3 times that of the same dimension in the photo....so....if the area of the photo = L x W the area of the painting = 3L x 3L = 9[W x L]......9 times as much....!!!!