Finding the Fourth Proportional to 1,216.68, 1,678.98 and 685.58

Step by Step Solution

1. Step 1: Write the proportion equation
   1,216.68 : 1,678.98 = 685.58 : x
2. Step 2: Convert to fraction form
   1,216.68/1,678.98 = 685.58/x
3. Step 3: Cross multiply
   1,216.68x = 1,678.98 × 685.58
4. Step 4: Simplify right side
   1,216.68x = 1,151,066.71
5. Step 5: Solve for x
   x = 1,151,066.71/1,216.68
6. Step 6: Final answer
   x = 946.07