Finding the Fourth Proportional to 1,078.29, 1,613.35 and 639.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,078.29 : 1,613.35 = 639.78 : x
2. Step 2: Convert to fraction form
   1,078.29/1,613.35 = 639.78/x
3. Step 3: Cross multiply
   1,078.29x = 1,613.35 × 639.78
4. Step 4: Simplify right side
   1,078.29x = 1,032,189.06
5. Step 5: Solve for x
   x = 1,032,189.06/1,078.29
6. Step 6: Final answer
   x = 957.25