Finding the Third Proportional to 10,638 and 12,420

Step by Step Solution

1. Step 1: Write the proportion equation
   10,638 : 12,420 = 12,420 : x
2. Step 2: Convert to fraction form
   10,638/12,420 = 12,420/x
3. Step 3: Cross multiply
   10,638x = 12,420 × 12,420
4. Step 4: Simplify right side
   10,638x = 154,256,400
5. Step 5: Solve for x
   x = 154,256,400/10,638
6. Step 6: Final answer
   x = 14,500.51