Finding the Third Proportional to 8,721 and 12,799.50

Step by Step Solution

1. Step 1: Write the proportion equation
   8,721 : 12,799.50 = 12,799.50 : x
2. Step 2: Convert to fraction form
   8,721/12,799.50 = 12,799.50/x
3. Step 3: Cross multiply
   8,721x = 12,799.50 × 12,799.50
4. Step 4: Simplify right side
   8,721x = 163,827,200.25
5. Step 5: Solve for x
   x = 163,827,200.25/8,721
6. Step 6: Final answer
   x = 18,785.37