Finding the Third Proportional to 390,519 and 812,137.50

Step by Step Solution

1. Step 1: Write the proportion equation
   390,519 : 812,137.50 = 812,137.50 : x
2. Step 2: Convert to fraction form
   390,519/812,137.50 = 812,137.50/x
3. Step 3: Cross multiply
   390,519x = 812,137.50 × 812,137.50
4. Step 4: Simplify right side
   390,519x = 659,567,318,906.25
5. Step 5: Solve for x
   x = 659,567,318,906.25/390,519
6. Step 6: Final answer
   x = 1,688,950.65