Four concentric circles are drawn with radii of 1, 3, 5 and 7. The inner circle is painted black, the ring around it is white, the next ring is black and the outer ring is white. What is the ratio of the black area to the white area? Express your answer as a common fraction.
+592 the area of the black shaded region is:$\pi+25\pi-9\pi=17\pi$
the area of the white shaded region is:$9\pi-\pi+49\pi-25\pi=32\pi$
therefore, the ratio of the black area to white area is $\boxed{\frac{17}{32}}$
