Finding the Fourth Proportional to 12,978.60, 19,470.42 and 5,188.20

Step by Step Solution

1. Step 1: Write the proportion equation
   12,978.60 : 19,470.42 = 5,188.20 : x
2. Step 2: Convert to fraction form
   12,978.60/19,470.42 = 5,188.20/x
3. Step 3: Cross multiply
   12,978.60x = 19,470.42 × 5,188.20
4. Step 4: Simplify right side
   12,978.60x = 101,016,433.04
5. Step 5: Solve for x
   x = 101,016,433.04/12,978.60
6. Step 6: Final answer
   x = 7,783.31