Finding the Third Proportional to 9,900 and 12,870

Step by Step Solution

1. Step 1: Write the proportion equation
   9,900 : 12,870 = 12,870 : x
2. Step 2: Convert to fraction form
   9,900/12,870 = 12,870/x
3. Step 3: Cross multiply
   9,900x = 12,870 × 12,870
4. Step 4: Simplify right side
   9,900x = 165,636,900
5. Step 5: Solve for x
   x = 165,636,900/9,900
6. Step 6: Final answer
   x = 16,731