Finding the Fourth Proportional to 3,928.05, 5,421.98 and 2,515.55

Step by Step Solution

1. Step 1: Write the proportion equation
   3,928.05 : 5,421.98 = 2,515.55 : x
2. Step 2: Convert to fraction form
   3,928.05/5,421.98 = 2,515.55/x
3. Step 3: Cross multiply
   3,928.05x = 5,421.98 × 2,515.55
4. Step 4: Simplify right side
   3,928.05x = 13,639,261.79
5. Step 5: Solve for x
   x = 13,639,261.79/3,928.05
6. Step 6: Final answer
   x = 3,472.27