Finding the Fourth Proportional to 100,978.72, 139,356.72 and 55,656.64

Step by Step Solution

1. Step 1: Write the proportion equation
   100,978.72 : 139,356.72 = 55,656.64 : x
2. Step 2: Convert to fraction form
   100,978.72/139,356.72 = 55,656.64/x
3. Step 3: Cross multiply
   100,978.72x = 139,356.72 × 55,656.64
4. Step 4: Simplify right side
   100,978.72x = 7,756,126,796.62
5. Step 5: Solve for x
   x = 7,756,126,796.62/100,978.72
6. Step 6: Final answer
   x = 76,809.52