Finding the Fourth Proportional to 21,085.20, 29,111.00 and 13,139.10

Step by Step Solution

1. Step 1: Write the proportion equation
   21,085.20 : 29,111.00 = 13,139.10 : x
2. Step 2: Convert to fraction form
   21,085.20/29,111.00 = 13,139.10/x
3. Step 3: Cross multiply
   21,085.20x = 29,111.00 × 13,139.10
4. Step 4: Simplify right side
   21,085.20x = 382,492,274.40
5. Step 5: Solve for x
   x = 382,492,274.40/21,085.20
6. Step 6: Final answer
   x = 18,140.32