Finding the Fourth Proportional to 390,500.18, 585,081.61 and 213,131.65

Step by Step Solution

1. Step 1: Write the proportion equation
   390,500.18 : 585,081.61 = 213,131.65 : x
2. Step 2: Convert to fraction form
   390,500.18/585,081.61 = 213,131.65/x
3. Step 3: Cross multiply
   390,500.18x = 585,081.61 × 213,131.65
4. Step 4: Simplify right side
   390,500.18x = 124,699,405,998.55
5. Step 5: Solve for x
   x = 124,699,405,998.55/390,500.18
6. Step 6: Final answer
   x = 319,332.52