Finding the Fourth Proportional to 3,900.12, 5,382.16 and 2,131.72

Step by Step Solution

1. Step 1: Write the proportion equation
   3,900.12 : 5,382.16 = 2,131.72 : x
2. Step 2: Convert to fraction form
   3,900.12/5,382.16 = 2,131.72/x
3. Step 3: Cross multiply
   3,900.12x = 5,382.16 × 2,131.72
4. Step 4: Simplify right side
   3,900.12x = 11,473,274.03
5. Step 5: Solve for x
   x = 11,473,274.03/3,900.12
6. Step 6: Final answer
   x = 2,941.78