Finding the Fourth Proportional to 13,615.88, 18,788.50 and 9,138.72

Step by Step Solution

1. Step 1: Write the proportion equation
   13,615.88 : 18,788.50 = 9,138.72 : x
2. Step 2: Convert to fraction form
   13,615.88/18,788.50 = 9,138.72/x
3. Step 3: Cross multiply
   13,615.88x = 18,788.50 × 9,138.72
4. Step 4: Simplify right side
   13,615.88x = 171,702,840.72
5. Step 5: Solve for x
   x = 171,702,840.72/13,615.88
6. Step 6: Final answer
   x = 12,610.48