We know that this is a question about scale factors. Since the original painting is 24 in. wide, and the width of the postcard reduction of the painting is 3 in., we can find the scale factor (assuming the postcard is to scale). We can find the scale factor by dividing the copy by the original, or 3 divided by 24, which means that the scale factor is 1/8. Now, to find the length of the postcard, we need to multiply the original dimension, 32 in., by 1/8, our scale factor. Doing that gives us that the length of the postcard is 4 in.
