Finding the Fourth Proportional to 978.78, 1,350.63 and 685.02

Step by Step Solution

1. Step 1: Write the proportion equation
   978.78 : 1,350.63 = 685.02 : x
2. Step 2: Convert to fraction form
   978.78/1,350.63 = 685.02/x
3. Step 3: Cross multiply
   978.78x = 1,350.63 × 685.02
4. Step 4: Simplify right side
   978.78x = 925,208.56
5. Step 5: Solve for x
   x = 925,208.56/978.78
6. Step 6: Final answer
   x = 945.27