Finding the Fourth Proportional to 1,216.53, 1,678.76 and 685.47

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.53 : 1,678.76 = 685.47 : x
2. Step 2: Convert to fraction form
   1,216.53/1,678.76 = 685.47/x
3. Step 3: Cross multiply
   1,216.53x = 1,678.76 × 685.47
4. Step 4: Simplify right side
   1,216.53x = 1,150,745.06
5. Step 5: Solve for x
   x = 1,150,745.06/1,216.53
6. Step 6: Final answer
   x = 945.92