Finding the Fourth Proportional to 1,128.56, 1,557.36 and 686.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.56 : 1,557.36 = 686.72 : x
2. Step 2: Convert to fraction form
   1,128.56/1,557.36 = 686.72/x
3. Step 3: Cross multiply
   1,128.56x = 1,557.36 × 686.72
4. Step 4: Simplify right side
   1,128.56x = 1,069,474.15
5. Step 5: Solve for x
   x = 1,069,474.15/1,128.56
6. Step 6: Final answer
   x = 947.65