Finding the Fourth Proportional to 789.12, 1,086.24 and 685.56

Step by Step Solution

1. Step 1: Write the proportion equation
   789.12 : 1,086.24 = 685.56 : x
2. Step 2: Convert to fraction form
   789.12/1,086.24 = 685.56/x
3. Step 3: Cross multiply
   789.12x = 1,086.24 × 685.56
4. Step 4: Simplify right side
   789.12x = 744,682.69
5. Step 5: Solve for x
   x = 744,682.69/789.12
6. Step 6: Final answer
   x = 943.69