Finding the Third Proportional to 9,920 and 12,640

Step by Step Solution

1. Step 1: Write the proportion equation
   9,920 : 12,640 = 12,640 : x
2. Step 2: Convert to fraction form
   9,920/12,640 = 12,640/x
3. Step 3: Cross multiply
   9,920x = 12,640 × 12,640
4. Step 4: Simplify right side
   9,920x = 159,769,600
5. Step 5: Solve for x
   x = 159,769,600/9,920
6. Step 6: Final answer
   x = 16,105.81