Finding the Fourth Proportional to 1,078.68, 1,488.77 and 636.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.68 : 1,488.77 = 636.55 : x
2. Step 2: Convert to fraction form
   1,078.68/1,488.77 = 636.55/x
3. Step 3: Cross multiply
   1,078.68x = 1,488.77 × 636.55
4. Step 4: Simplify right side
   1,078.68x = 947,676.54
5. Step 5: Solve for x
   x = 947,676.54/1,078.68
6. Step 6: Final answer
   x = 878.55