An equilateral triangle is placed inside a larger equilateral triangle so that the region between them can be divided into three congruent trapezoids, as shown below. The side length of the inner triangle is \dfrac{2}{3} the side length of the larger triangle. What is the ratio of the area of one trapezoid to the area of the inner triangle?
Answer Choices
A. 1:3
B. 3:8
C. 5:12
D. 7:16
E. 4:9