Finding the Fourth Proportional to 1,078.90, 1,488.50 and 636.70

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.90 : 1,488.50 = 636.70 : x
2. Step 2: Convert to fraction form
   1,078.90/1,488.50 = 636.70/x
3. Step 3: Cross multiply
   1,078.90x = 1,488.50 × 636.70
4. Step 4: Simplify right side
   1,078.90x = 947,727.95
5. Step 5: Solve for x
   x = 947,727.95/1,078.90
6. Step 6: Final answer
   x = 878.42