Finding the Fourth Proportional to 1,507.78, 2,259.78 and 858.88

Step by Step Solution

1. Step 1: Write the proportion equation
   1,507.78 : 2,259.78 = 858.88 : x
2. Step 2: Convert to fraction form
   1,507.78/2,259.78 = 858.88/x
3. Step 3: Cross multiply
   1,507.78x = 2,259.78 × 858.88
4. Step 4: Simplify right side
   1,507.78x = 1,940,879.85
5. Step 5: Solve for x
   x = 1,940,879.85/1,507.78
6. Step 6: Final answer
   x = 1,287.24