Finding the Third Proportional to 3,991.50 and 8,665.50

Step by Step Solution

1. Step 1: Write the proportion equation
   3,991.50 : 8,665.50 = 8,665.50 : x
2. Step 2: Convert to fraction form
   3,991.50/8,665.50 = 8,665.50/x
3. Step 3: Cross multiply
   3,991.50x = 8,665.50 × 8,665.50
4. Step 4: Simplify right side
   3,991.50x = 75,090,890.25
5. Step 5: Solve for x
   x = 75,090,890.25/3,991.50
6. Step 6: Final answer
   x = 18,812.70