Finding the Fourth Proportional to 388,215.05, 535,722.76 and 216,128.59

Step by Step Solution

1. Step 1: Write the proportion equation
   388,215.05 : 535,722.76 = 216,128.59 : x
2. Step 2: Convert to fraction form
   388,215.05/535,722.76 = 216,128.59/x
3. Step 3: Cross multiply
   388,215.05x = 535,722.76 × 216,128.59
4. Step 4: Simplify right side
   388,215.05x = 115,785,003,874.56
5. Step 5: Solve for x
   x = 115,785,003,874.56/388,215.05
6. Step 6: Final answer
   x = 298,249.66