Finding the Fourth Proportional to 15,856.21, 21,881.41 and 8,686.18

Step by Step Solution

1. Step 1: Write the proportion equation
   15,856.21 : 21,881.41 = 8,686.18 : x
2. Step 2: Convert to fraction form
   15,856.21/21,881.41 = 8,686.18/x
3. Step 3: Cross multiply
   15,856.21x = 21,881.41 × 8,686.18
4. Step 4: Simplify right side
   15,856.21x = 190,065,865.91
5. Step 5: Solve for x
   x = 190,065,865.91/15,856.21
6. Step 6: Final answer
   x = 11,986.84