Finding the Fourth Proportional to 1,128.16, 1,556.43 and 685.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.16 : 1,556.43 = 685.90 : x
2. Step 2: Convert to fraction form
   1,128.16/1,556.43 = 685.90/x
3. Step 3: Cross multiply
   1,128.16x = 1,556.43 × 685.90
4. Step 4: Simplify right side
   1,128.16x = 1,067,547.55
5. Step 5: Solve for x
   x = 1,067,547.55/1,128.16
6. Step 6: Final answer
   x = 946.28