Finding the Fourth Proportional to 21,085.68, 29,111.70 and 13,139.56

Step by Step Solution

1. Step 1: Write the proportion equation
   21,085.68 : 29,111.70 = 13,139.56 : x
2. Step 2: Convert to fraction form
   21,085.68/29,111.70 = 13,139.56/x
3. Step 3: Cross multiply
   21,085.68x = 29,111.70 × 13,139.56
4. Step 4: Simplify right side
   21,085.68x = 382,514,928.85
5. Step 5: Solve for x
   x = 382,514,928.85/21,085.68
6. Step 6: Final answer
   x = 18,140.98