Finding the Third Proportional to 8,728 and 13,139

Step by Step Solution

1. Step 1: Write the proportion equation
   8,728 : 13,139 = 13,139 : x
2. Step 2: Convert to fraction form
   8,728/13,139 = 13,139/x
3. Step 3: Cross multiply
   8,728x = 13,139 × 13,139
4. Step 4: Simplify right side
   8,728x = 172,633,321
5. Step 5: Solve for x
   x = 172,633,321/8,728
6. Step 6: Final answer
   x = 19,779.25