Finding the Third Proportional to 128,788.50 and 280,457.50

Step by Step Solution

1. Step 1: Write the proportion equation
   128,788.50 : 280,457.50 = 280,457.50 : x
2. Step 2: Convert to fraction form
   128,788.50/280,457.50 = 280,457.50/x
3. Step 3: Cross multiply
   128,788.50x = 280,457.50 × 280,457.50
4. Step 4: Simplify right side
   128,788.50x = 78,656,409,306.25
5. Step 5: Solve for x
   x = 78,656,409,306.25/128,788.50
6. Step 6: Final answer
   x = 610,740.94