Finding the Fourth Proportional to 13,106.72, 18,087.60 and 7,138.72

Step by Step Solution

1. Step 1: Write the proportion equation
   13,106.72 : 18,087.60 = 7,138.72 : x
2. Step 2: Convert to fraction form
   13,106.72/18,087.60 = 7,138.72/x
3. Step 3: Cross multiply
   13,106.72x = 18,087.60 × 7,138.72
4. Step 4: Simplify right side
   13,106.72x = 129,122,311.87
5. Step 5: Solve for x
   x = 129,122,311.87/13,106.72
6. Step 6: Final answer
   x = 9,851.61