Finding the Third Proportional to 8,400 and 12,820

Step by Step Solution

1. Step 1: Write the proportion equation
   8,400 : 12,820 = 12,820 : x
2. Step 2: Convert to fraction form
   8,400/12,820 = 12,820/x
3. Step 3: Cross multiply
   8,400x = 12,820 × 12,820
4. Step 4: Simplify right side
   8,400x = 164,352,400
5. Step 5: Solve for x
   x = 164,352,400/8,400
6. Step 6: Final answer
   x = 19,565.76