Finding the Fourth Proportional to 1,216.39, 1,678.66 and 685.48

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.39 : 1,678.66 = 685.48 : x
2. Step 2: Convert to fraction form
   1,216.39/1,678.66 = 685.48/x
3. Step 3: Cross multiply
   1,216.39x = 1,678.66 × 685.48
4. Step 4: Simplify right side
   1,216.39x = 1,150,690.81
5. Step 5: Solve for x
   x = 1,150,690.81/1,216.39
6. Step 6: Final answer
   x = 945.99