Finding the Third Proportional to 8,404 and 12,780

Step by Step Solution

1. Step 1: Write the proportion equation
   8,404 : 12,780 = 12,780 : x
2. Step 2: Convert to fraction form
   8,404/12,780 = 12,780/x
3. Step 3: Cross multiply
   8,404x = 12,780 × 12,780
4. Step 4: Simplify right side
   8,404x = 163,328,400
5. Step 5: Solve for x
   x = 163,328,400/8,404
6. Step 6: Final answer
   x = 19,434.60