Finding the Fourth Proportional to 13,089.60, 18,061.20 and 7,785.72

Step by Step Solution

1. Step 1: Write the proportion equation
   13,089.60 : 18,061.20 = 7,785.72 : x
2. Step 2: Convert to fraction form
   13,089.60/18,061.20 = 7,785.72/x
3. Step 3: Cross multiply
   13,089.60x = 18,061.20 × 7,785.72
4. Step 4: Simplify right side
   13,089.60x = 140,619,446.06
5. Step 5: Solve for x
   x = 140,619,446.06/13,089.60
6. Step 6: Final answer
   x = 10,742.84