Finding the Fourth Proportional to 13,688.53, 18,887.72 and 7,720.18

Step by Step Solution

1. Step 1: Write the proportion equation
   13,688.53 : 18,887.72 = 7,720.18 : x
2. Step 2: Convert to fraction form
   13,688.53/18,887.72 = 7,720.18/x
3. Step 3: Cross multiply
   13,688.53x = 18,887.72 × 7,720.18
4. Step 4: Simplify right side
   13,688.53x = 145,816,512.37
5. Step 5: Solve for x
   x = 145,816,512.37/13,688.53
6. Step 6: Final answer
   x = 10,652.46