Finding the Fourth Proportional to 138,638.72, 208,074.72 and 129,890.72

Step by Step Solution

1. Step 1: Write the proportion equation
   138,638.72 : 208,074.72 = 129,890.72 : x
2. Step 2: Convert to fraction form
   138,638.72/208,074.72 = 129,890.72/x
3. Step 3: Cross multiply
   138,638.72x = 208,074.72 × 129,890.72
4. Step 4: Simplify right side
   138,638.72x = 27,026,975,194.60
5. Step 5: Solve for x
   x = 27,026,975,194.60/138,638.72
6. Step 6: Final answer
   x = 194,945.36