Finding the Fourth Proportional to 390,870.30, 528,089.63 and 390,870.30

Step by Step Solution

1. Step 1: Write the proportion equation
   390,870.30 : 528,089.63 = 390,870.30 : x
2. Step 2: Convert to fraction form
   390,870.30/528,089.63 = 390,870.30/x
3. Step 3: Cross multiply
   390,870.30x = 528,089.63 × 390,870.30
4. Step 4: Simplify right side
   390,870.30x = 206,414,552,104.99
5. Step 5: Solve for x
   x = 206,414,552,104.99/390,870.30
6. Step 6: Final answer
   x = 528,089.63