Finding the Fourth Proportional to 1,216.59, 1,678.86 and 685.46

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.59 : 1,678.86 = 685.46 : x
2. Step 2: Convert to fraction form
   1,216.59/1,678.86 = 685.46/x
3. Step 3: Cross multiply
   1,216.59x = 1,678.86 × 685.46
4. Step 4: Simplify right side
   1,216.59x = 1,150,795.57
5. Step 5: Solve for x
   x = 1,150,795.57/1,216.59
6. Step 6: Final answer
   x = 945.92