Finding the Third Proportional to 318,138 and 686,089.50

Step by Step Solution

1. Step 1: Write the proportion equation
   318,138 : 686,089.50 = 686,089.50 : x
2. Step 2: Convert to fraction form
   318,138/686,089.50 = 686,089.50/x
3. Step 3: Cross multiply
   318,138x = 686,089.50 × 686,089.50
4. Step 4: Simplify right side
   318,138x = 470,718,802,010.25
5. Step 5: Solve for x
   x = 470,718,802,010.25/318,138
6. Step 6: Final answer
   x = 1,479,605.71