Finding the Fourth Proportional to 3,978.10, 5,979.30 and 3,905.20

Step by Step Solution

1. Step 1: Write the proportion equation
   3,978.10 : 5,979.30 = 3,905.20 : x
2. Step 2: Convert to fraction form
   3,978.10/5,979.30 = 3,905.20/x
3. Step 3: Cross multiply
   3,978.10x = 5,979.30 × 3,905.20
4. Step 4: Simplify right side
   3,978.10x = 23,350,362.36
5. Step 5: Solve for x
   x = 23,350,362.36/3,978.10
6. Step 6: Final answer
   x = 5,869.73