Finding the Third Proportional to 390,091.50 and 811,111.50

Step by Step Solution

1. Step 1: Write the proportion equation
   390,091.50 : 811,111.50 = 811,111.50 : x
2. Step 2: Convert to fraction form
   390,091.50/811,111.50 = 811,111.50/x
3. Step 3: Cross multiply
   390,091.50x = 811,111.50 × 811,111.50
4. Step 4: Simplify right side
   390,091.50x = 657,901,865,432.25
5. Step 5: Solve for x
   x = 657,901,865,432.25/390,091.50
6. Step 6: Final answer
   x = 1,686,532.17