Finding the Fourth Proportional to 839.69, 1,258.71 and 429.02

Step by Step Solution

1. Step 1: Write the proportion equation
   839.69 : 1,258.71 = 429.02 : x
2. Step 2: Convert to fraction form
   839.69/1,258.71 = 429.02/x
3. Step 3: Cross multiply
   839.69x = 1,258.71 × 429.02
4. Step 4: Simplify right side
   839.69x = 540,005.47
5. Step 5: Solve for x
   x = 540,005.47/839.69
6. Step 6: Final answer
   x = 643.10