Finding the Fourth Proportional to 128,608.50, 177,479.82 and 72,021.18

Step by Step Solution

1. Step 1: Write the proportion equation
   128,608.50 : 177,479.82 = 72,021.18 : x
2. Step 2: Convert to fraction form
   128,608.50/177,479.82 = 72,021.18/x
3. Step 3: Cross multiply
   128,608.50x = 177,479.82 × 72,021.18
4. Step 4: Simplify right side
   128,608.50x = 12,782,306,062.59
5. Step 5: Solve for x
   x = 12,782,306,062.59/128,608.50
6. Step 6: Final answer
   x = 99,389.28