Finding the Fourth Proportional to 20,980.50, 31,475.61 and 7,129.50

Step by Step Solution

1. Step 1: Write the proportion equation
   20,980.50 : 31,475.61 = 7,129.50 : x
2. Step 2: Convert to fraction form
   20,980.50/31,475.61 = 7,129.50/x
3. Step 3: Cross multiply
   20,980.50x = 31,475.61 × 7,129.50
4. Step 4: Simplify right side
   20,980.50x = 224,405,361.50
5. Step 5: Solve for x
   x = 224,405,361.50/20,980.50
6. Step 6: Final answer
   x = 10,695.90