Finding the Fourth Proportional to 390,492.43, 585,069.99 and 213,123.89

Step by Step Solution

1. Step 1: Write the proportion equation
   390,492.43 : 585,069.99 = 213,123.89 : x
2. Step 2: Convert to fraction form
   390,492.43/585,069.99 = 213,123.89/x
3. Step 3: Cross multiply
   390,492.43x = 585,069.99 × 213,123.89
4. Step 4: Simplify right side
   390,492.43x = 124,692,392,854.52
5. Step 5: Solve for x
   x = 124,692,392,854.52/390,492.43
6. Step 6: Final answer
   x = 319,320.90