Finding the Fourth Proportional to 5,291.71, 7,921.98 and 3,911.20

Step by Step Solution

1. Step 1: Write the proportion equation
   5,291.71 : 7,921.98 = 3,911.20 : x
2. Step 2: Convert to fraction form
   5,291.71/7,921.98 = 3,911.20/x
3. Step 3: Cross multiply
   5,291.71x = 7,921.98 × 3,911.20
4. Step 4: Simplify right side
   5,291.71x = 30,984,428.37
5. Step 5: Solve for x
   x = 30,984,428.37/5,291.71
6. Step 6: Final answer
   x = 5,855.28