Finding the Fourth Proportional to 3,947.18, 5,470.15 and 3,891.50

Step by Step Solution

1. Step 1: Write the proportion equation
   3,947.18 : 5,470.15 = 3,891.50 : x
2. Step 2: Convert to fraction form
   3,947.18/5,470.15 = 3,891.50/x
3. Step 3: Cross multiply
   3,947.18x = 5,470.15 × 3,891.50
4. Step 4: Simplify right side
   3,947.18x = 21,287,069.27
5. Step 5: Solve for x
   x = 21,287,069.27/3,947.18
6. Step 6: Final answer
   x = 5,392.98