Finding the Fourth Proportional to 1,128.77, 1,557.24 and 686.60

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.77 : 1,557.24 = 686.60 : x
2. Step 2: Convert to fraction form
   1,128.77/1,557.24 = 686.60/x
3. Step 3: Cross multiply
   1,128.77x = 1,557.24 × 686.60
4. Step 4: Simplify right side
   1,128.77x = 1,069,200.98
5. Step 5: Solve for x
   x = 1,069,200.98/1,128.77
6. Step 6: Final answer
   x = 947.23