Finding the Fourth Proportional to 1,159.78, 1,739.59 and 429.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,159.78 : 1,739.59 = 429.31 : x
2. Step 2: Convert to fraction form
   1,159.78/1,739.59 = 429.31/x
3. Step 3: Cross multiply
   1,159.78x = 1,739.59 × 429.31
4. Step 4: Simplify right side
   1,159.78x = 746,823.38
5. Step 5: Solve for x
   x = 746,823.38/1,159.78
6. Step 6: Final answer
   x = 643.94