Finding the Third Proportional to 13,638 and 20,856

Step by Step Solution

1. Step 1: Write the proportion equation
   13,638 : 20,856 = 20,856 : x
2. Step 2: Convert to fraction form
   13,638/20,856 = 20,856/x
3. Step 3: Cross multiply
   13,638x = 20,856 × 20,856
4. Step 4: Simplify right side
   13,638x = 434,972,736
5. Step 5: Solve for x
   x = 434,972,736/13,638
6. Step 6: Final answer
   x = 31,894.17