Finding the Fourth Proportional to 1,078.61, 1,488.60 and 636.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.61 : 1,488.60 = 636.50 : x
2. Step 2: Convert to fraction form
   1,078.61/1,488.60 = 636.50/x
3. Step 3: Cross multiply
   1,078.61x = 1,488.60 × 636.50
4. Step 4: Simplify right side
   1,078.61x = 947,493.90
5. Step 5: Solve for x
   x = 947,493.90/1,078.61
6. Step 6: Final answer
   x = 878.44