Finding the Third Proportional to 390,411 and 530,320.50

Step by Step Solution

1. Step 1: Write the proportion equation
   390,411 : 530,320.50 = 530,320.50 : x
2. Step 2: Convert to fraction form
   390,411/530,320.50 = 530,320.50/x
3. Step 3: Cross multiply
   390,411x = 530,320.50 × 530,320.50
4. Step 4: Simplify right side
   390,411x = 281,239,832,720.25
5. Step 5: Solve for x
   x = 281,239,832,720.25/390,411
6. Step 6: Final answer
   x = 720,368.62