Finding the Third Proportional to 7,978 and 12,820

Step by Step Solution

1. Step 1: Write the proportion equation
   7,978 : 12,820 = 12,820 : x
2. Step 2: Convert to fraction form
   7,978/12,820 = 12,820/x
3. Step 3: Cross multiply
   7,978x = 12,820 × 12,820
4. Step 4: Simplify right side
   7,978x = 164,352,400
5. Step 5: Solve for x
   x = 164,352,400/7,978
6. Step 6: Final answer
   x = 20,600.70