The side lengths of △WXY are 21, 27, and 45 units. The length of the longest side of △CDE is 15 units. If △WXY and △CDE are similar, what is the length of the shortest side of △CDE?

To solve this problem, we need to find the ratio of the sides of the two similar triangles.

Step 1: Identify the longest side of △WXY, which is 45 units.

Step 2: The longest side of △CDE is 15 units.

Step 3: Find the ratio of the sides of △CDE to △WXY by dividing the length of the longest side of △CDE by the length of the longest side of △WXY. This gives us 15/45 = 1/3.

Step 4: The shortest side of △WXY is 21 units.

Step 5: To find the length of the shortest side of △CDE, multiply the length of the shortest side of △WXY by the ratio we found in step 3. This gives us 21 * (1/3) = 7 units.

So, the length of the shortest side of △CDE is 7 units.