Finding the Fourth Proportional to 1,078.70, 1,488.71 and 636.74

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.70 : 1,488.71 = 636.74 : x
2. Step 2: Convert to fraction form
   1,078.70/1,488.71 = 636.74/x
3. Step 3: Cross multiply
   1,078.70x = 1,488.71 × 636.74
4. Step 4: Simplify right side
   1,078.70x = 947,921.21
5. Step 5: Solve for x
   x = 947,921.21/1,078.70
6. Step 6: Final answer
   x = 878.76