Finding the Fourth Proportional to 5,145.21, 7,721.60 and 3,978.09

Step by Step Solution

1. Step 1: Write the proportion equation
   5,145.21 : 7,721.60 = 3,978.09 : x
2. Step 2: Convert to fraction form
   5,145.21/7,721.60 = 3,978.09/x
3. Step 3: Cross multiply
   5,145.21x = 7,721.60 × 3,978.09
4. Step 4: Simplify right side
   5,145.21x = 30,717,199.85
5. Step 5: Solve for x
   x = 30,717,199.85/5,145.21
6. Step 6: Final answer
   x = 5,970.06