Finding the Fourth Proportional to 15,513.42, 21,407.89 and 8,439.87

Step by Step Solution

1. Step 1: Write the proportion equation
   15,513.42 : 21,407.89 = 8,439.87 : x
2. Step 2: Convert to fraction form
   15,513.42/21,407.89 = 8,439.87/x
3. Step 3: Cross multiply
   15,513.42x = 21,407.89 × 8,439.87
4. Step 4: Simplify right side
   15,513.42x = 180,679,808.57
5. Step 5: Solve for x
   x = 180,679,808.57/15,513.42
6. Step 6: Final answer
   x = 11,646.68