Finding the Third Proportional to 9,978 and 20,990

Step by Step Solution

1. Step 1: Write the proportion equation
   9,978 : 20,990 = 20,990 : x
2. Step 2: Convert to fraction form
   9,978/20,990 = 20,990/x
3. Step 3: Cross multiply
   9,978x = 20,990 × 20,990
4. Step 4: Simplify right side
   9,978x = 440,580,100
5. Step 5: Solve for x
   x = 440,580,100/9,978
6. Step 6: Final answer
   x = 44,155.15