Finding the Fourth Proportional to 100,450.38, 138,621.78 and 55,128.72

Step by Step Solution

1. Step 1: Write the proportion equation
   100,450.38 : 138,621.78 = 55,128.72 : x
2. Step 2: Convert to fraction form
   100,450.38/138,621.78 = 55,128.72/x
3. Step 3: Cross multiply
   100,450.38x = 138,621.78 × 55,128.72
4. Step 4: Simplify right side
   100,450.38x = 7,642,041,295.52
5. Step 5: Solve for x
   x = 7,642,041,295.52/100,450.38
6. Step 6: Final answer
   x = 76,077.77