Finding the Fourth Proportional to 390,499.31, 538,938.95 and 218,426.83

Step by Step Solution

1. Step 1: Write the proportion equation
   390,499.31 : 538,938.95 = 218,426.83 : x
2. Step 2: Convert to fraction form
   390,499.31/538,938.95 = 218,426.83/x
3. Step 3: Cross multiply
   390,499.31x = 538,938.95 × 218,426.83
4. Step 4: Simplify right side
   390,499.31x = 117,718,723,972.55
5. Step 5: Solve for x
   x = 117,718,723,972.55/390,499.31
6. Step 6: Final answer
   x = 301,456.94