Finding the Fourth Proportional to 1,128.15, 1,556.90 and 685.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.15 : 1,556.90 = 685.78 : x
2. Step 2: Convert to fraction form
   1,128.15/1,556.90 = 685.78/x
3. Step 3: Cross multiply
   1,128.15x = 1,556.90 × 685.78
4. Step 4: Simplify right side
   1,128.15x = 1,067,690.88
5. Step 5: Solve for x
   x = 1,067,690.88/1,128.15
6. Step 6: Final answer
   x = 946.41