Finding the Fourth Proportional to 1,128.65, 1,557.59 and 686.28

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.65 : 1,557.59 = 686.28 : x
2. Step 2: Convert to fraction form
   1,128.65/1,557.59 = 686.28/x
3. Step 3: Cross multiply
   1,128.65x = 1,557.59 × 686.28
4. Step 4: Simplify right side
   1,128.65x = 1,068,939.43
5. Step 5: Solve for x
   x = 1,068,939.43/1,128.65
6. Step 6: Final answer
   x = 947.10