Finding the Fourth Proportional to 10,128.78, 13,978.42 and 5,653.40

Step by Step Solution

1. Step 1: Write the proportion equation
   10,128.78 : 13,978.42 = 5,653.40 : x
2. Step 2: Convert to fraction form
   10,128.78/13,978.42 = 5,653.40/x
3. Step 3: Cross multiply
   10,128.78x = 13,978.42 × 5,653.40
4. Step 4: Simplify right side
   10,128.78x = 79,025,571.36
5. Step 5: Solve for x
   x = 79,025,571.36/10,128.78
6. Step 6: Final answer
   x = 7,802.08