Finding the Fourth Proportional to 20,081.71, 30,128.87 and 12,085.21

Step by Step Solution

1. Step 1: Write the proportion equation
   20,081.71 : 30,128.87 = 12,085.21 : x
2. Step 2: Convert to fraction form
   20,081.71/30,128.87 = 12,085.21/x
3. Step 3: Cross multiply
   20,081.71x = 30,128.87 × 12,085.21
4. Step 4: Simplify right side
   20,081.71x = 364,113,636.17
5. Step 5: Solve for x
   x = 364,113,636.17/20,081.71
6. Step 6: Final answer
   x = 18,131.60