Final answer:
The ratio of the areas of Rectangle A to B is 16 to 81.
Step-by-step explanation:
The ratio of the side lengths of Rectangle A to Rectangle B is 4 to 9. To find the ratio of their areas, square the side length ratio.
The area of Rectangle A is equal to the length multiplied by the width, which is 4 times the smaller side length.
The area of Rectangle B is equal to the length multiplied by the width, which is 9 times the smaller side length.
So, the ratio of their areas is 16 to 81.