Finding the Fourth Proportional to 13,697.21, 18,902.72 and 7,728.89

Step by Step Solution

1. Step 1: Write the proportion equation
   13,697.21 : 18,902.72 = 7,728.89 : x
2. Step 2: Convert to fraction form
   13,697.21/18,902.72 = 7,728.89/x
3. Step 3: Cross multiply
   13,697.21x = 18,902.72 × 7,728.89
4. Step 4: Simplify right side
   13,697.21x = 146,096,968.39
5. Step 5: Solve for x
   x = 146,096,968.39/13,697.21
6. Step 6: Final answer
   x = 10,666.18