Finding the Fourth Proportional to 3,820.56, 5,726.40 and 3,128.40

Step by Step Solution

1. Step 1: Write the proportion equation
   3,820.56 : 5,726.40 = 3,128.40 : x
2. Step 2: Convert to fraction form
   3,820.56/5,726.40 = 3,128.40/x
3. Step 3: Cross multiply
   3,820.56x = 5,726.40 × 3,128.40
4. Step 4: Simplify right side
   3,820.56x = 17,914,469.76
5. Step 5: Solve for x
   x = 17,914,469.76/3,820.56
6. Step 6: Final answer
   x = 4,688.96