Finding the Fourth Proportional to 1,078.56, 1,487.34 and 685.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.56 : 1,487.34 = 685.80 : x
2. Step 2: Convert to fraction form
   1,078.56/1,487.34 = 685.80/x
3. Step 3: Cross multiply
   1,078.56x = 1,487.34 × 685.80
4. Step 4: Simplify right side
   1,078.56x = 1,020,017.77
5. Step 5: Solve for x
   x = 1,020,017.77/1,078.56
6. Step 6: Final answer
   x = 945.72