Finding the Fourth Proportional to 100,729.76, 138,978.84 and 64,940.72

Step by Step Solution

1. Step 1: Write the proportion equation
   100,729.76 : 138,978.84 = 64,940.72 : x
2. Step 2: Convert to fraction form
   100,729.76/138,978.84 = 64,940.72/x
3. Step 3: Cross multiply
   100,729.76x = 138,978.84 × 64,940.72
4. Step 4: Simplify right side
   100,729.76x = 9,025,385,934.36
5. Step 5: Solve for x
   x = 9,025,385,934.36/100,729.76
6. Step 6: Final answer
   x = 89,599.99