Finding the Third Proportional to 15,900 and 21,099

Step by Step Solution

1. Step 1: Write the proportion equation
   15,900 : 21,099 = 21,099 : x
2. Step 2: Convert to fraction form
   15,900/21,099 = 21,099/x
3. Step 3: Cross multiply
   15,900x = 21,099 × 21,099
4. Step 4: Simplify right side
   15,900x = 445,167,801
5. Step 5: Solve for x
   x = 445,167,801/15,900
6. Step 6: Final answer
   x = 27,997.97