Finding the Fourth Proportional to 3,900.60, 5,850.50 and 978.90

Step by Step Solution

1. Step 1: Write the proportion equation
   3,900.60 : 5,850.50 = 978.90 : x
2. Step 2: Convert to fraction form
   3,900.60/5,850.50 = 978.90/x
3. Step 3: Cross multiply
   3,900.60x = 5,850.50 × 978.90
4. Step 4: Simplify right side
   3,900.60x = 5,727,049.56
5. Step 5: Solve for x
   x = 5,727,049.56/3,900.60
6. Step 6: Final answer
   x = 1,468.25