Finding the Fourth Proportional to 1,216.48, 1,678.54 and 685.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.48 : 1,678.54 = 685.30 : x
2. Step 2: Convert to fraction form
   1,216.48/1,678.54 = 685.30/x
3. Step 3: Cross multiply
   1,216.48x = 1,678.54 × 685.30
4. Step 4: Simplify right side
   1,216.48x = 1,150,303.46
5. Step 5: Solve for x
   x = 1,150,303.46/1,216.48
6. Step 6: Final answer
   x = 945.60