Finding the Third Proportional to 9,990 and 20,560.50

Step by Step Solution

1. Step 1: Write the proportion equation
   9,990 : 20,560.50 = 20,560.50 : x
2. Step 2: Convert to fraction form
   9,990/20,560.50 = 20,560.50/x
3. Step 3: Cross multiply
   9,990x = 20,560.50 × 20,560.50
4. Step 4: Simplify right side
   9,990x = 422,734,160.25
5. Step 5: Solve for x
   x = 422,734,160.25/9,990
6. Step 6: Final answer
   x = 42,315.73