Finding the Fourth Proportional to 7,123.89, 9,831.15 and 3,980.28

Step by Step Solution

1. Step 1: Write the proportion equation
   7,123.89 : 9,831.15 = 3,980.28 : x
2. Step 2: Convert to fraction form
   7,123.89/9,831.15 = 3,980.28/x
3. Step 3: Cross multiply
   7,123.89x = 9,831.15 × 3,980.28
4. Step 4: Simplify right side
   7,123.89x = 39,130,729.72
5. Step 5: Solve for x
   x = 39,130,729.72/7,123.89
6. Step 6: Final answer
   x = 5,492.89