Finding the Fourth Proportional to 3,899.61, 5,381.57 and 2,131.31

Step by Step Solution

1. Step 1: Write the proportion equation
   3,899.61 : 5,381.57 = 2,131.31 : x
2. Step 2: Convert to fraction form
   3,899.61/5,381.57 = 2,131.31/x
3. Step 3: Cross multiply
   3,899.61x = 5,381.57 × 2,131.31
4. Step 4: Simplify right side
   3,899.61x = 11,469,793.96
5. Step 5: Solve for x
   x = 11,469,793.96/3,899.61
6. Step 6: Final answer
   x = 2,941.27