Finding the Fourth Proportional to 12,686.31, 19,031.29 and 3,921.91

Step by Step Solution

1. Step 1: Write the proportion equation
   12,686.31 : 19,031.29 = 3,921.91 : x
2. Step 2: Convert to fraction form
   12,686.31/19,031.29 = 3,921.91/x
3. Step 3: Cross multiply
   12,686.31x = 19,031.29 × 3,921.91
4. Step 4: Simplify right side
   12,686.31x = 74,638,891.80
5. Step 5: Solve for x
   x = 74,638,891.80/12,686.31
6. Step 6: Final answer
   x = 5,883.42